1. Tardigrade
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  3. Mathematics
  4. A man saves ` 135 in the first year, ` 150 in the second year and in this way he increases his savings by ` 15 every, year. In what time will his total saving be ` 5550?

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Q. A man saves ` 135 in the first year, ` 150 in the second year and in this way he increases his savings by ` 15 every, year. In what time will his total saving be ` 5550?

JamiaJamia 2011

Solution:

Let the required time be n years. $ \therefore $ $ 5550=135+150+...+n $ terms $ =\frac{n}{2}[2\times 135+(n-1)15] $ $ \Rightarrow $ $ 2\times 5550=270n+n(n-1)15 $ $ \Rightarrow $ $ 740=18n+{{n}^{2}}-n $ $ \Rightarrow $ $ {{n}^{2}}+17n-740=0 $ $ \Rightarrow $ $ (n-20)(n+37)=0 $ $ \Rightarrow $ $ n=20\,yr $ ( $ \because $ $ n $ cannot be negative)