X purchased some pens for TK. 120 . If the price per piece of pen was TK. 3 less, he would have received 2 more pens. How many pens did he purchase ?
Created: 6 years ago |
Updated: 2 years ago
best des
Let the number of pens be N.
Then, price of each pen = 120/N
He would get (N + 2) pens if the price of each pen was [120/N - 3].
So, 120 / (N + 2) = (120/N) - 3
or, 120 / (N + 2) = (120 - 3N) / N
or, 120N = (120 - 3N) (N + 2)
or, 120N = 120N + 120 x 2 - 3N2 - 3N x 2
or, 3N2 + 6N + 120N - 120N - 240 = 0
or, 3N2 + 6N - 240 = 0
or, N2 + 2N - 80 = 0
or, N2 + 10N - 8N - 80 = 0
or, N(N + 10) - 8(N + 10) = 0
or, (N + 10) (N - 8) = 0
or, N - 8 = 0 [N + 10 = / 0]
So, N = 8
Md Azizur Rahman
Founder of Satt
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