Question

William's, Eva's, and Dave's savings every month are in the ratio 3:5:4. If Eva saves 2400 in a month,
how much do William and Dave save?​

Answer 1

Answer:

A man saves Rs 200 in very first month and he saves Rs 25 more in every next month.

Suppose it takes n number of months to save Rs 13325.

So according to the situation,we get the sequence of his savings as,

200,225,250,275,.......................13325

Here in the above arithmetic sequence,

First term, a=200

Common difference,d=25

Sum of the given series,S = 13325

We know that,

Sum of an arithmetic sequence is,

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

=> 13325 = (n/2){ 2×200 + (n - 1)×25}

=> 13325 = (n/2) { 400 + (n - 1)×25}

=> 13325 = (n/2) (400 - 25 + 25n)

=> 13325 × 2 = n(25n +375)

=> 25 n^2 + 375 n = 26650

=> n^2 + 15 n - 1066 = 0

=> n^2 + 41n - 26n - 1066 = 0

=> n(n + 41) -26 (n + 41)

=> (n - 26) (n + 41) = 0

=> n = 26 or n = - 41

Since n is the number of months it takes to collect Rs 13325,so it can not be negative.

● So in 26 months,that man will save Rs 13325.

Answer 2

Answer:

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