Question 42

When $$7^{21} + 7^{22} + 7^{23} + 7^{24}$$ is divided by 25 the remainder is:

Solution

Given, $$7^{21} + 7^{22} + 7^{23} + 7^{24}$$

= $$7^{21}( 1 + 7 + 49 + 343)$$

= $$7^{21}(400)$$

Now, 400 is divisible by 25. The remainder will be 0

Hence, option D is the correct answer.

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