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Hi ajaymahadev

What do you mean by \(R(\frac{78}{4})=0\)?

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Hi ajaymahadev

What do you mean by \(R(\frac{78}{4})=0\)?

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Careless mistake from my part. Sorry. The remainder of 78/4 is 2. Edited the answer. The answer is 4.
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The official answer is wrong. The answer is 4.

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GMATinsight
Find the unit digit of

\(72^{72}*73^{73}*74^{74}*76^{76}*77^{77}*78^{78}\)

A) 2
B) 4
c) 6
D) 8
E) None of these

Source: https://www.GMATinsight.com

\(72^{4*18}*73^{18*4+1}*74^{2*37}*76^{76}*77^{4*19+1}*78^{4*19+2}\)

72^4k = Will have units digit as 6
73^4k will have units digit 1 * 73 = Units digit 3
74^2k will have units digit as 6
76^k will have units digit as 6
77^4k will have units digit as 1 * 7 = Units digit 7
78^4k will have units digit as 6 * 4 = units 4

Multiply all 6*3*6*6*7*4 = 4 Units digit, Answer must be (B)
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