Question

find the square of 85 containing 5 in units place​

Answer 1

Answer:

(i) 15 (ii) 95 (iii) 105 (iv) 205

(i) (15)2 = 1 x (1 + 1) x 100 + 25

= 1 x 2 x 100 + 25

= 200 + 25 = 225

(ii) (95)2 = 9 x (9 + 1) x 100 + 25

= 9 x 10 x 100 + 25

= 9000 + 25 = 9025

(iii)

(105)2 = 10 x (10 + 1) x 100 + 25

= 10 x 11 x 100 + 25

= 11000 + 25 = 11025

(iv)

(205)2 = 20 x (20 + 1) x 100 + 25

= 20 x 21 x 100 + 25

= 42000 + 25 = 42025