Question

If the c.d of an A.P is 4, then find the value of a15 – a10

Answer 1

Answer:

a + 14d - a + 9d = 23d = 23 × 4 = 92

Answer 2

$a_{15}-a_{10}$ = 20

Step-by-step explanation:

Given,

The common difference of an AP (d) = 4

Let the first term = a

To find, $a_{15}-a_{10}$ = ?

We know that,

The nth term of an AP

$a_{n}$ = a + (n - 1)d

∴ The 15th term of an AP

$a_{15}$ = a + (15 - 1)d = a + 14d

The 10th term of an AP

$a_{10}$ = a + (10 - 1)d = a + 9d

∴ $a_{15}-a_{10}$

= a + 14d - (a + 9d)

= a + 14d - a - 9d

= 5d

Put d = 4, we get

= 5(4)

= 20

∴ $a_{15}-a_{10}$ = 20