The average of a, b, c is 6 and a-b = 4, ab = 21, what is the value of c ?
Created: 6 years ago |
Updated: 2 years ago
best des
Here, a - b = 4
or, a = b + 4 - - - - - - (i)
Again, ab = 21
or, (b + 4)b = 21 [from (i)]
or, b2 + 4b - 21 = 0
or. b2 + 7b - 3b - 21 = 0
or, b(b + 7) - 3(b + 7) = 0
or, (b + 7) (b - 3) = 0
or, b - 3 = 0 [b ≠ - 7]
So, b = 3.
Now, a + b + c = 6 x 3
or, a + b + c = 18
or, b + 4 + b + c = 18 [from(i)]
or, 3 + 4 + 3 + c = 18
or, c = 18 - 10 = 8
Md Azizur Rahman
Founder of Satt
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