Question

The first term of an Arithmetic progression is 5 and last term is45 If the sum of the terms is 125 then find the numbers of terms​

Answer 1

Answer

Given that, First term of an arithmetic progression is 5. (a = 5)

The last term is 45. (l = 45)

The sum of the terms is 125. (Sn = 125)

We have to find the number of terms means 'n'.

We know that,

Sn = n/2 (a + l)

Substitute the given values in the above formula

→ 125 = n/2 (5 + 45)

→ 125 = n/2 (50)

→ 125 = n(25)

→ 125/25 = n

→ 25/5 = n

→ 5 = n

Therefore,

Number of terms = n = 5

Verification:

Substitute value of n = 5 in 125 = n/2 (5 + 45)

→ 125 = 5/2 (5 + 45)

→ 125 = 5/2 (50)

→ 125 = 5(25)

→ 125 = 125

Step-by-step explanation:

Answer 2

Sn = n/2 (a+l)

125 = n/2 (5+45)

250 = 50n

5 = n

5 no of terms are there