A) 21 months
B) 18 months
C) 19 months
D) 20 months
Correct Answer: A
Solution :
Total savings \[=200+200+200+240+280+....\] to n months = 11040 \[\Rightarrow 400+\frac{n-2}{2}\left( 400+\left( n-3 \right).40 \right)=11040\] \[\Rightarrow (n-2)(140+20n)=10640\] \[\Rightarrow 20{{n}^{2}}+100n-280=10640\] \[\Rightarrow {{n}^{2}}+5n-546=0\] \[\Rightarrow (n=21)(n+26)=0\] \[\Rightarrow n=21\] as \[n\ne -26\]You need to login to perform this action.
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