You can see that an odd number of steps is simply multiplying the number of steps by a number that moves up one each time. For instance, 1*1, 3*2, 5*3, etc. It's a bit harder with the even numbers. Their pattern is multiplying half the number of steps by 1.5, but the ones place value moves up a number each time, for example, 2*1.5, 4*2.5, 6*3.5. This means that 10 steps is 10 * 5.5, or 55 blocks and that 100 is 5,050 steps.
Explanation If ‘a’ represents his age today, and you have to find his age in four years you take 4 multiplied a. (4 x a) putting it together and you would get 4a