Question

how many terms added 24+20+16+...... to make the sum of 72
​

Answer 1

Answer:

Step-by-step explanation:

Given A.P is 24,20,16,...

so, the first term, a=24

the common difference, d=20−24

=−4.

The sum of first n terms of A.P is given by

2

n

​

[2a+(n−1)d]=

2

n

​

[48−(n−1)4]

Given, the sum is 72.

so,  

2

n

​

[48−(n−1)4]=72

⇒24n−n(n−1)2=72

⇒2n

2

−26n+72=0⇒n

2

−13n+36=0

⇒n=4 or 9.

∴ 4 terms and 9 terms add upto 72.

I HOPE IT HELPS YOU

Answer 2

Answer:

Step-by-step explanation:

24+20+16+x=72

60 +x = 72

X= 72 -60

X= 12