Question

Tell me the answer In steps​

Answer 1

A certain number is not known. We name it $x$ and calculate the value. First, let's understand the situation.

$\dfrac{3x}{14}$ is the value he needs to find. But, by mistake, he found $\dfrac{3x}{4}$, which was 150 more than the expected answer.

By adding 150 to the found value, we get the expected answer.

$\implies\dfrac{3x}{14}+150=\dfrac{3x}{4}$

Let's solve this equation. If we multiply/divide(should be nonzero)/add/subtract all numbers by the same value, the equation gives the same value of the number, since both numbers go through the same operations.

We eliminate the denominator by multiplying 28.

$\implies \dfrac{3x}{14}\times28+150\times28=\dfrac{3x}{4}\times28$

$\implies 6x+4200=21x$

Let's subtract $6x$ from both numbers.

$\implies 6x-6x+4200=21x-6x$

$\implies 15x=4200$

We get the answer by dividing by $-15$ from both numbers.

$\implies x=\dfrac{4200}{15}$

$\implies x=280$

As said above, we chose $x$ as the number. So, the original number 280 leaves the correct option (d).