I like to reduce everything by half if I don't already know the answer.

It just so happens that is the reduced fraction.
All I did was halve 18, which is 9, and halve 34, which is 17.
this is false not all equations and all equations are identities are same
2(x-2)=6
2x-4=6
2x=6+4
2x/2=10/2
x=5
So, the sphere went from 1.2 meters to 1.4 meters.
The radius will always be half of the diameter. So it went from .6 to .7.
Let's divide and see what percent .7 is of .6.
.7÷.6=1.166666666(repeating 6).
This means, it increased by about 16.7%, since it was not doubling, just going up.