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digits 71*72*

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by eaakbari » Thu Apr 15, 2010 3:38 am
what are the last two digits of the expression 71*72*73*... and so on till 79?


a50
b 70
c 00
d 80


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Source: — Problem Solving |

by liferocks » Thu Apr 15, 2010 7:01 am
the ans will be divisible by 100 as the numbers has 75=25x3 as well as 4 in it.
hence last 2 digits will be [spoiler]C) 00[/spoiler]
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by hachette » Thu Apr 15, 2010 7:08 am
75 x 4 = 300
the last two digits are 00
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by eaakbari » Thu Apr 15, 2010 8:38 am
Oh yes, I am silly, took 75 as a single 5. Thanks guys
Whether you think you can or can't, you're right.
- Henry Ford
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by Ashish8 » Thu Apr 15, 2010 10:14 am
This is how I did it as I didn't understand hachette or liferocks.

Someone can correct me if its the wrong approach

We know 74 * 75 will yield one 0 at the end. The last two digits will be 50.

50 * 76 will yield two 0's at the end. After that everything will yield 2 0's at the end.
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