Numerical reasoning 3 / 8,15 / 24,35 / 48, ()

Numerical reasoning 3 / 8,15 / 24,35 / 48, ()

It's 1 * 3, 3 * 5, 5 * 7, 7 * 9
Here are 2 * 4, 4 * 6, 6 * 8, 8 * 10
Answer: see above