A man saved 32 rs during first year, 36 rs in second year and in this way. He increases his saving by rupees 4 every year. Find in what time his saving will be 200 rs
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Answer:
In 5 years a man saving will be ₹ 200.
Step-by-step explanation:
Given :
In first year a man saved, a = ₹ 32
In second year a man saved , a2 = ₹ 36
Increase in savings, d = 36 - 32 = 4
His saving in 'n' years will be , Sn = 200
Let 'n' be the number of years.
By using the formula ,Sum of nth terms , Sn = n/2 [2a + (n – 1) d]
200 = n/2 [2 × 32 + (n– 1)4]
200 × 2 = n[64 + 4(n - 1)]
400 = n[64 + 4n - 4]
400 = n[60 + 4n]
400 = 4n[15 + n]
400/4 = 15n + n²
100 = 15n + n²
n² + 15n – 100 = 0
n² + 20n – 5n – 100 = 0
[By middle term splitting]
n (n + 20) – 5 (n + 20) = 0
(n – 5) (n + 20) = 0
(n – 5) = 0, n = 5 & (n + 20) = 0, n = - 20
Number of years can never be negative. Therefore, n = 5
Hence, in 5 years a man saving will be ₹ 200.
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