Question

Among all pairs of numbers with a sum of 105 , find the pair whose product is maximum. Write your answers as fractions reduced to lowest terms.

Answer 1

Answer: Hence Pair( x, y) = [ 105/2, 105/2]

Explanation:

Given that;

Among all pairs of numbers with a sum of 105;

the pair whose product is maximum = ?

so let pairs of numbers with a sum of 105 be x and y respectively

x + y = 105

let y = 105 - x

now

product = xy = x( 105 - x ) = 105x - x²

now

p(x) = 105x - x²

for maximum value of p

dp/dx =0

⇒ dp/dx = 105 - 2x = 0

2x = 105

x = 105/2

y + x = 105

y = 105 - x

y = 105 - 105/2 = 105/2

Hence Pair( x, y) = [ 105/2, 105/2]