# Thrice the Square of a Natural Number Decreased by 4 Times the Number is Equal to 50 more than the Number. The Number is?

### Computer MCQs Series for PPSC, FPSC – Most Repeated MCQs | Set 6

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## Explanation

• Thrice the square of a natural number decreased by 4 times the number.
• Is equal to 50 more than the number.

The number can be figure out in this way.

Let suppose the number is y.

Thrice the square of “y” decreased by 4y

3y2 – 4y

3y2 – 4y is equal to 50 more than the number

3y2 – 4y = y + 50 ________ (i)

Through equation (i) we can easily find out the value of y (y = 5).

Number = ?

## Solution

Let suppose

Number = y

According to the given condition

3y2 – 4y = y + 50

3y2 – 4y – y – 50 = 0

3y2 – 5y – 50 = 0

3y2 – 15y + 10y – 50 = 0

3y(y – 5) + 10(y – 5) = 0

(3y + 10)(y – 5) = 0

3y + 10 = 0                   &                y – 5 = 0

y = -10/3 (not possible)                 &                y = 5 (possible)

## Conclusion

Thrice the square of a natural number decreased by 4 times, the number is equal to 50 more than the number. The number is 5.