
<PAGE>
 
                                                                  Exhibit (A)(7)

This announcement is neither an offer to purchase nor a solicitation of an offer
to sell Shares. The Offer is made solely by the Offer to Purchase, dated April
15, 1998, and the related Letter of Transmittal and any amendments or
supplements thereto, and is being made to all holders of Shares. The Offer is
not being made to (nor will tenders be accepted from or on behalf of) holders of
Shares in any jurisdiction in which the making of the Offer or the acceptance
thereof would not be in compliance with the laws of such jurisdiction. In any
jurisdiction where the securities, blue sky or other laws require the Offer to
be made by a licensed broker or dealer, the Offer shall be deemed to be made on
behalf of DGC Acquisition, Inc., by Donaldson, Lufkin & Jenrette Securities
Corporation or one or more registered brokers or dealers licensed under the laws
of such jurisdiction.

                      Notice of Offer to Purchase for Cash
                     All Outstanding Shares of Common Stock
                                       of
                             Dart Group Corporation
                                       at
                             $160.00 Net Per Share
                                       by
                              DGC Acquisition, Inc.
                       a direct wholly-owned subsidiary of
                             Richfood Holdings, Inc.

         DGC Acquisition, Inc., a Delaware corporation ("Purchaser") and a
direct wholly-owned subsidiary of Richfood Holdings, Inc., a Virginia
corporation ("Parent"), is offering to purchase all outstanding shares of common
stock, $1.00 par value per share (the "Shares"), of Dart Group Corporation, a
Delaware corporation (the "Company"), at a price of $160.00 per Share (the
"Offer Price"), net to the seller in cash, upon the terms and subject to the
conditions set forth in the Offer to Purchase, dated April 15, 1998, and in the
related Letter of Transmittal (which, together with any amendments or
supplements thereto, collectively constitute the "Offer"). Tendering
stockholders will not be obligated to pay brokerage fees or commissions or,
except as set forth in Instruction 6 of the Letter of Transmittal, transfer
taxes on the purchase of Shares pursuant to the Offer. The purpose of the Offer
is to acquire for cash as many outstanding Shares as possible as a first step in
acquiring the entire equity interest in the Company. Following consummation of
the Offer, Purchaser intends to effect the merger described below.

        THE OFFER AND WITHDRAWAL RIGHTS WILL EXPIRE AT 12:00 MIDNIGHT, 
  NEW YORK CITY TIME, ON TUESDAY, MAY 12, 1998, UNLESS THE OFFER IS EXTENDED.

         The Offer is conditioned upon, among other things, (1) a number of the
Shares representing a majority of all outstanding Shares on a fully diluted
basis being validly tendered and not withdrawn prior to the expiration of the
Offer, and (2) the expiration of certain waiting periods under the
Hart-Scott-Rodino Antitrust Improvements Act of 1976, as amended.

         The Offer is being made pursuant to an Agreement and Plan of Merger,
dated as of April 9, 1998 (the "Merger Agreement"), among Parent, Purchaser and
the Company. The Merger Agreement provides, among other things, for the
commencement of the Offer by Purchaser and further provides that after the
purchase of Shares pursuant to the Offer, subject to the satisfaction or waiver
of certain conditions, Purchaser will be merged with and into the Company (the
"Merger"), with the Company surviving the Merger as a direct wholly-owned
subsidiary of Parent. At the effective time of the Merger, each outstanding
Share (other than Shares owned by the Company or any wholly-owned subsidiary of
the Company or by Parent, Purchaser or any other wholly-owned subsidiary of
Parent, and Shares owned by stockholders who shall have properly exercised their
appraisal rights under Delaware law) will be converted into the right to receive
$160.00 in cash or any greater amount paid pursuant to the Offer, without
interest.

         The Board of Directors of the Company (the "Board") has unanimously
determined that the Offer and the Merger are fair to, and in the best interests
of, the Company and its stockholders, has approved the Merger Agreement and the
transactions contemplated by the Merger Agreement, including the Offer and the
Merger,
<PAGE>
 
and recommends that the Company's stockholders accept the Offer and tender all
of their Shares pursuant thereto.

         For purposes of the Offer, Purchaser will be deemed to have accepted
for payment (and thereby purchased) tendered Shares as, if and when Purchaser
gives oral or written notice to First Union National Bank (the "Depositary") of
its acceptance of such Shares for payment pursuant to the Offer. Upon the terms
and subject to the conditions of the Offer, payment for Shares purchased
pursuant to the Offer will be made by deposit of the purchase price therefor
with the Depositary, which will act as agent for tendering stockholders for the
purposes of receiving payment from Purchaser and transmitting payment to
tendering stockholders whose Shares have theretofore been accepted for payment.
In all cases, payment for Shares purchased pursuant to the Offer will be made
only after timely receipt by the Depositary of (i) certificates for (or a timely
Book-Entry Confirmation (as defined in Section 3 of the Offer to Purchase) with
respect to) such Shares, (ii) the Letter of Transmittal (or a manually signed
facsimile thereof), properly completed and duly executed with all required
signature guarantees or an agent's message, and (iii) all other documents
required by the Letter of Transmittal. Under no circumstances will interest be
paid on the purchase price for Shares to be paid by Purchaser, regardless of any
delay in making such payment.

         The term "Expiration Date" shall mean 12:00 midnight, New York City
time, on Tuesday, May 12, 1998, unless and until Purchaser, in accordance with
the terms of the Offer and the Merger Agreement, shall have extended the period
of time during which the Offer is open, in which event the term "Expiration
Date" shall mean the latest time and date at which the Offer, as so extended by
Purchaser, shall expire. Subject to the terms of the Merger Agreement and
applicable law, Purchaser expressly reserves the right, at any time or from time
to time, to extend the period of time during which the Offer is open and, in
certain circumstances, may be required to extend the Offer until June 30, 1998,
and thereby delay acceptance for payment of, or payment for, any Shares by
giving oral or written notice of such extension to the Depositary and by making
a public announcement of such extension. Purchaser shall not have any obligation
to pay interest on the purchase price for tendered Shares whether or not
Purchaser exercises its right to extend the period of time during which the
Offer is open. Any such extension will be followed by a public announcement
thereof no later than 9:00 a.m., New York City time, on the next business day
after the previously scheduled Expiration Date. During any such extension, all
Shares previously tendered and not withdrawn will remain subject to the Offer,
subject to the right of a tendering stockholder to withdraw such stockholder's
Shares. Without limiting the manner in which Purchaser may choose to make any
public announcement, Purchaser will have no obligation to publish, advertise or
otherwise communicate any such announcement other than by issuing a release to
the Dow Jones News Service or as otherwise may be required by law.

         Except as otherwise provided in the Offer to Purchase, tenders of
Shares are irrevocable. Shares tendered pursuant to the Offer may be withdrawn
at any time prior to the Expiration Date and, unless theretofore accepted for
payment by Purchaser as provided for in the Offer to Purchase, may also be
withdrawn at any time after Saturday, June 13, 1998. For a withdrawal to be
effective, a written, telegraphic or facsimile transmission notice of withdrawal
must be timely received by the Depositary at its address set forth on the back
cover of the Offer to Purchase. Any such notice of withdrawal must specify the
name of the person who tendered the Shares to be withdrawn, the number of Shares
to be withdrawn and the name of the registered holder, if different from that of
the person who tendered such Shares. If certificates evidencing Shares have been
delivered or otherwise identified to the Depositary, then, prior to the release
of such certificates, the tendering stockholder must also submit the serial
numbers shown on the particular certificates evidencing the Shares to be
withdrawn, and the signature on the notice of withdrawal must be guaranteed by
an Eligible Institution, as defined in Section 3 of the Offer to Purchase
(except in the case of Shares tendered for the account of an Eligible
Institution). If Shares have been tendered pursuant to the procedure for
book-entry transfer set forth in Section 3 of the Offer to Purchase, the notice
of withdrawal must specify the name and number of the account at the applicable
Book-Entry Transfer Facility (as defined in Section 3 of the Offer to Purchase)
to be credited with the withdrawn Shares. All questions as to the form and
validity (including time of receipt) of notices of withdrawal will be determined
by Purchaser, in its sole discretion, whose determination shall be final and
binding on all parties. Any Shares properly withdrawn will be deemed not validly
tendered for purposes of the Offer, but may be tendered at any subsequent time
prior to the Expiration Date by following any of the procedures described in
Section 3 of the Offer to Purchase.
<PAGE>
 
         The Company has provided Purchaser with the Company's stockholder list
and security position listings for the purpose of disseminating the Offer to
holders of Shares. The Offer to Purchase, the related Letter of Transmittal and,
if required, any other relevant materials will be mailed to record holders of
Shares and will be furnished to brokers, dealers, commercial banks, trust
companies and similar persons whose names, or the name of whose nominees, appear
on the Company's stockholders list or, if applicable, who are listed as
participants in a clearing agency's security position listing, for subsequent
transmittal to beneficial owners of Shares by Purchaser.

         The information required to be disclosed by paragraph (e)(1)(vii) of
Rule 14d-6 of the General Rules and Regulations under the Securities Exchange
Act of 1934, as amended, is contained in the Offer to Purchase and is
incorporated herein by reference.

         The Offer to Purchase and the related Letter of Transmittal contain
important information which should be read carefully before any decision is made
with respect to the Offer.

         Requests for copies of the Offer to Purchase, the Letter of Transmittal
and other tender offer documents may be directed to the Information Agent as set
forth below, and copies will be furnished promptly at Purchaser's expense.
Questions or requests for assistance may be directed to the Information Agent or
the Dealer Manager. Neither Purchaser nor Parent will pay any fees or
commissions to any broker or dealer or other person (other than the Dealer
Manager, the Depositary and the Information Agent) in connection with the
solicitation of tenders of Shares pursuant to the Offer. 

                    The Information Agent for the Offer is:
                    CORPORATE INVESTOR COMMUNICATIONS, INC.

                               111 Commerce Road
                           Carlstadt, NJ 07072-2586

                 Banks and Brokers call collect (201) 896-1900
                   All others call toll free: (888) 520-2226

                      The Dealer Manager for the Offer is:

               DONALDSON, LUFKIN & JENRETTE SECURITIES CORPORATION

                                 277 Park Avenue
                            New York, New York 10172
                          (877) 893-0576 (toll free)

                                (212) 892-8017

April 15, 1998
