Wednesday, August 12, 2009

Question of the day - 12th August

Question:

What is the unit digit of 1007*1034*1221*15343*100009*10034*1091*1191*1233?

a. 6
b. 0
c. 4
d. 2
e. 8

Finding answer to this question should not take more than 15-20 secs. If you spend more than half a min than you need to check out the idea behind this question. Solution with the shortcut will be posted in about 12 hrs time in this blog while in other forums it will be posted in 24 hrs time.

Thanks,
Quant-Master
Posted by GMAT at 11:59 PM

2 comments:

  1. GMATAugust 13, 2009 at 10:38 PM

    OA is D

    Like mentioned by other users above, the idea is to multiply only the unit digits of each number.

    1007*1034*1221*15343*100009*10034*1091*1191*1233

    multiply 7*4 =28 (forget 2, take only 8)
    multiply 8*3= 24 (I ignored the 3rd number as unit digit of that number is 1 and 1 multiplied by any number is that number)
    multiply 4*9 = 36
    multiply 6*4 = 24
    multiply 4*3 =12 (I ignored 1 again). Hence unit digit is 2

    Thanks,
    Quant-Master

    ReplyDelete
  2. MalayAugust 13, 2009 at 11:17 PM

    1007*1034*1221*15343*100009*10034*1091*1191*1233? answer to this is 2

    ReplyDelete

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