gibran Posted June 26, 2008 Share Posted June 26, 2008 What is the tens' digit and the units' digit of 123456789^2? OA: 21 Quote Link to comment Share on other sites More sharing options...
Creslin Posted June 26, 2008 Share Posted June 26, 2008 Yep, there's a very easy shortcut. You are only concerned about the tens and the units digit. When you multiply two integers, the only digits that can effect the tens and the units digits of the product are the tens and the units digits of the muliplier and the multiplicand. So ALL OF THE OTHER DIGITS CAN BE DISCARDED. 123456789^2 becomes 89^2. NONE OF THE OTHER DIGITS MATTER Just do the multiplication and the tens and units digits will be 21. Quote Link to comment Share on other sites More sharing options...
arindambanerji Posted June 27, 2008 Share Posted June 27, 2008 Just multiply the unit and tens digit..correct approach creslin Quote Link to comment Share on other sites More sharing options...
Makumajon Posted June 27, 2008 Share Posted June 27, 2008 123456789^2 = (123456700+89)^2 = (123456700)^2+2*123456700*89+89^2 = ********0000+ *******00+7921; [7921 = 7900+21] So, 21 is the result. Quote Link to comment Share on other sites More sharing options...
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