CAT Practice : Functions

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Function of a function

Q.14: For this question, assume the following operators: A*B = A2 - B2
A-B = $\frac{A}{B}$
A+B = A * B
$\frac{A}{B}$ = A+B
Which of the following expression would yield the result as x subtracted by y?

1. (x*y)-(x+5)
2. ($\frac{x}{y}$)*(x-y)
3. (x*y) - ($\frac{x}{y}$)
4. (x+y)*(x-y)

Choice C. (x*y) - ($\frac{x}{y}$)

Detailed Solution

Never solve each expression. Solve by assigning values of x and y

Let x = 6, y = 2 Therefore, required x – y = 4
x*y = 62 – 22 = 32

x-y = $\frac{6}{2}$ = 3

x+y = 6 x 2 = 12

$\frac{x}{y}$ = 6 + 2 = 8

a) 32-12 = $\frac{32}{12}$ not equal to 4

b) 8*3 = 82 - 32 = 55 not equal to 4

c) 32 - 8 = $\frac{32}{8}$ = 4

d) 12*3 = 122 - 32 not equal to 4

Correct Answer: (x*y) - ($\frac{x}{y}$)

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Functions.