Rob spent 25% extra percent on his project than the had planned.
Let us assume total number of hours spent x hours.
Given that he spent an extra h hours on the project
So, we could say 25% of x is h.
0.25 x = h.
Dividing both sides by 0.25.
We get 0.25h/0.25 = h/0.25.
x = h/0.25.
Let us convert 0.25 into fractions.
0.25 = 25/100 = 1/4.
Therefore,
x = h/1/4 = 4h.
Therefore, Rob planned 4h hours.
He spent h hours extra.
So, he spent total 4h+h = 5h hours total.