Practice | Hashtable

Home > Practice > Arithmetic Aptitude > Number System > Miscellaneous

1. The last digit of the number obtained by multiplying the numbers 81 × 82 × 83 × 84 × 86 × 87 × 88 × 89 will be

A. 0

B. 6

C. 7

D. 2

Solution:

The last digit of multiplication depends on the unit digit of (81 × 82 × 83 × 84 × 86 × 87 × 88 × 89) which is given by the remainder obtained on dividing it by 10.

\begin{aligned} \frac{(81 \times 82 \times 83 \times 84 \times 86 \times 87 \times 88 \times 89)}{10} \\ We take individual remainder of each digit, \\ \frac{(1 \times 2 \times 3 \times 4 \times 6 \times 7 \times 8 \times 9)}{10} \\ Numbers multiplied, \\ \frac{(24 \times 42 \times 72)}{10} \\ Individual Remainder has been taken, \\ \frac{(4 \times 2 \times 2)}{10} \\ O r, \frac{(16)}{10} \\ O r, 6 \\ Remainder = 6 \\ So, the last digit will be 6 \end{aligned}

You must login to add comments. Login now.