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by garuhape » Tue Mar 15, 2011 6:11 am
I've already solved this one ;)
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by coolly01 » Tue Mar 15, 2011 6:37 am
garuhape wrote:Hey Guys

What is the units digit of 3^17×17^54×135^19×31^21×42^17?

OA: 7

The unit digit is "0"
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by edvhou812 » Tue Mar 22, 2011 10:39 pm
3^17X17^54X135^19X31^21X42^1

Narrow things down to the last digit of each integer that appears, regardless of whether or not it is a whole number or exponent, and then multiply:

3X7X7X4X5x9x1x1x2x1 = 21x28x45x1x14 = 588x45x14 = 588x630 = 370,940

Units digit is the number to the far right: 0
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by Anurag@Gurome » Tue Mar 22, 2011 11:09 pm
garuhape wrote:What is the units digit of 3^17×17^54×135^19×31^21×42^17?
Just note that the unit's digit of 135^19 will be 5 and 42^17 is an even number. Hence the unit's digit of their product will be 0. Now, when any integer with zero as unit's digit is multiplied with any other integer, the unit's digit of the product will be always zero.

Therefore, unit's digit of the product is zero.

Please check the OA.
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