Maths : Basic Numeracy

Q 125 / 370

UPSC CSE Prelims 2022

When 70% of a number x is added to another number y, the sum becomes 165% of the value of y. When 60% of the number x is added to another number Z, then the sum becomes 165% of the value of z. Which one of the following is correct

EXPLANATION

Correct Option

The problem provides two relationships between three numbers x, y, and z.

From the first statement: "When 70% of a number x is added to another number y, the sum becomes 165% of the value of y."

This can be expressed as an equation:

0.7x+y=1.65y

Subtracting y from both sides yields:

0.7x=0.65y

From this, we can express y in terms of x:

y=0.70.65x=7065x=1413x

Since \frac{14}{13} > 1, it implies that y > x.

From the second statement: "When 60% of the number x is added to another number Z, then the sum becomes 165% of the value of z."

This can be expressed as an equation:

0.6x+z=1.65z

Subtracting z from both sides yields:

0.6x=0.65z

From this, we can express z in terms of x:

z=0.60.65x=6065x=1213x

Since \frac{12}{13} < 1, it implies that z < x.

Now, comparing y and z relative to x:

We have y=1413x and z=1213x.

Since \frac{14}{13} > \frac{12}{13}, it follows that y > z.

Combining the inequalities y > x, z < x, and y > z, the correct order is z < x < y.

Incorrect Options

Options 2, 3, and 4 are incorrect as they do not align with the derived order of the numbers z < x < y.