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The sum of the square of two numbers is 97 and the square of their difference is 25. The product of the two number is
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- 45
- 36
- 54
- 63
Correct Option: B
Let the two number are a and b
According to the question
sum of squares of two numbers = 97
i.e.., a 2 + b 2 = 97 .....................(i)
and square of their difference = 25
i.e., (a - b) 2 = 25 .................(ii)
⇒ a - b = 5...............(iii)
from Eq. (ii)
a2 + b2 - 2ab = 25
(a2 + b2) - 2ab = 25
Now put the value of a 2 + b 2 from Eq. (i)
⇒ 97 - 2ab = 25
⇒ 2ab = 72
⇒ ab = 36.................(iv)
Now, we have
(a + b)2 = ( a2 + b2) + 2ab
Now put the value of a 2 + b 2 from Eq. (i) and ab from Eq. (iv)
(a + b)2 = 97 + 72 = 169
a + b = 13.............(v)
Now add the Eqs. (iii) and (v), we get
a - b + a + b = 5 +13
2a = 18
⇒ a = 9
now put the value of a in Eq. (v)
a + b = 13
9 + b = 13
b = 13 - 9
b = 4
∴ Product of both the numbers = ab = 9 x 4 = 36