Question

Write the value of a50- a10 for the A.P. 1, 6, 11, 16.

Answer 1

a = 1

d = 5

A50 = a + 49d

= 1 + 49*5

= 1 + 245

= 246

A10 = a + 9d

= 1 + 9*5

= 1* 45

= 46

A50 - A10 = 246 - 46

= 200

Answer 2

a1 = 1
a2 = 6
d = a2-a1 = 6 -1 = 5
a50 - a10
= a + (50 - 1)d - [a + (10 - 1)d]
= 1 + 49 × 5 - [1 + 9 × 5]
= 246 - 46 = 200