Question

A man saves rs 32000 during first year , rs 36000 in the next year and rs 40000 in the third year . if he continues his savings in this sequence in how many years will be saves rs 200000​

Answer 1

Answer:

Step-by-step explanation:

so here we have to use concept of AP

where first term is 32000

second is 36000

and the third one is 40000

you can see the difference between the two term is 4000

hence we can take d=4000

and the last term i.e sum is 200000=Sn and first term as a=32000

hence using formula for sum

Sn=n/2 *(2a+(n-1)d)

200000=n/2(2*32000+(n-1)4000)

400000=n(64000+4000n-4000)

400000=n(60000+4000n)

400000=60000n+4000n²

4000n²+60000-400000=0

divide by 4000

n²+15n-100=0

n²+20n-5n-100=0

n(n+20)-5(n+20)=0

(n+20)(n-5)=0

hence n=-20 or n=5

year  can not be negative hence 5 is correct answer

he will save 200000 in 5 years

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Thank You....!