Question

How many terms of Arithmetic Progression,
17, 15, 13, 11, ........
must be added together so that their sum is equal to 72?
( Take the number of terms to be 'n' ).
Explain why the answer is having two values.

Answer the question only if you have studied Arithmetic Progression chapter in 10th std Textbook. Do not spam.​

Answer 1

Answer:

The common difference of this arithmetic progression is -2

Step-by-step explanation:

72 = (n/2) * (2a + (n-1)d), where a is the first term, n is the number of terms and d is the common difference

72 = (n/2) * ( (2*17) + (n-1)*(-2) )

72 = (n/2) * ( 34 -2n + 2)

144 = n * ( 34 -2n + 2)

144 = 36n -2n^2

2n^2 -36n +144 = 0

n^2 -18n +72 = 0

(n - 12) * (n - 6) = 0

Hope it helps u...!