model 4 finding unit place of a number Section-Wise Topic Notes With Detailed Explanation And Example Questions

Answer: (b)

$3^1 = 3; 3^2 = 9; 3^3 = 27;$

$3^4 = 81; 3^5 = 243 ;$ .....

Remainder on dividing 40 by 4 = 0

∴ Unit’s digit in $3^40$ = 1

Answer: (b)

Required unit’s digit = Unit’s digit in the product of 7 × 5 × 8 × 3 × 9 = 0

Answer: (a)

Unit digit in the expansion of $25^6251$

= Unit digit in the expansion of $5^6251$ = 5

$36^528$≡ Unit digit in $6^528$ = 6

Now, $3^1 = 3; 3^2 = 9; 3^3 = 27; 3^4 = 81; 3^5 = 243 ;$....

$73^54 = 73^52 × 73^2$≡ $3^2$ = 9

Required digit = Unit’s digit of the sum 5 + 6 + 9 = 0

Answer: (a)

Unit’s digit in 3 × 38 × 537 × 1256

= Unit’s digit in 3 × 8 × 7 × 6

= 4 × 2 = 8