Question 2

Find the unit place digit in 71 x 72 x 73 x 74 x 76 x 77 x 78 x 79.

Solution

Expression : 71 x 72 x 73 x 74 x 76 x 77 x 78 x 79

Unit place is the product of unit digits.

= $$(1\times2\times3\times4)\times(6\times7)\times(8\times9)$$

= $$24\times42\times72$$

$$\equiv4\times2\times2=16$$

Thus, unit digit = 6

=> Ans - (D)

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