Practicing Success

Target Exam

CUET

Subject

General Test

Chapter

Quantitative Reasoning

Topic

Algebra

Question:

If the difference between two numbers is 5 and the difference between the in cubes is 1850, then the difference between their squares is:

Options:

$5\sqrt{484}$

$5\sqrt{482}$

$5\sqrt{485}$

$5\sqrt{483}$

Correct Answer:

$5\sqrt{485}$

Explanation:

Let the numbers be x and y

According to the question,

x - y = 5

x³ - y³ = 1850

We know that,

(a - b)3 = a3 - b3 - 3ab(a-b)

(5)3 = 1850 - 3ab(5)

125 = 1850 - 15ab

15ab = 1725

ab = 115

We also know that,

If x - y  = n

then, x + y  = \(\sqrt {n^2 + 4xy}\)

then, x + y  = \(\sqrt {5^2 + 4(115)}\)

x + y  = \(\sqrt {5^2 + 4(115)}\)

x + y  = \(\sqrt {485}\)

The difference between their squares is = x2 - y2 = (x + y)(x - Y)

= x2 - y2 = $5\sqrt{485}$