Question

answer me plzzzzz......​

Answer 1

Sum = 3250

n2[40+(n−1)×15]=3250n2[40+(n−1)×15]=3250

on simplifying we get,

15n2+25n−6500⟹3n2+5n−1300⟹(n−20)(3n+65)∴n=0=0=0=20
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Answer 2

Answer:

20 months

Step-by-step explanation:

this question forms an AP

where, a = 20

d = 15

and sn = 3250

sn = n/2 (2a + (n-1)d)

⇒3250 = n/2 (2×20 + (n-1) 15)

⇒15n² + 25n - 6500= 0

⇒n= 20 or -65/3

-65/3 is not possible as time can not be negative

therefore answer is 20 months