Use mental math to determine the value of 15/124 x 230/30 : 230/124

We can usually simplify in the head. Start with the difficult ones, like 230 and 124.

15/124 x 230/30 : 230/124

We see that the first 124 is a denominator, and after flipping the division, 124 is at the top, so they cancel out.

Similarly, 230 is a numerator and after flipping the division, 230 is a denominator, so again they cancel out.

We then collect only terms that remain, namely

15/30 which simplifies to half, or 1/2.