Question

how many terms of the A.P.24,21,18.... must be taken so that their sum is 78?

Answer 1

The answer is 13.

Please mark brainliest!!

Answer 2

Sn= n/2{2a+(n-1)d}

78=n/2{2×24+(n-1)-3}

78=n/2{48+(n-1)-3}

78=n/2{48-3n+3}

78=n/2(51-3n)

156=n(51-3n)

156=51n-3n™

3n™-51n+156=0( solve this equation yourself plzzz)