You have the formula.
KE= 0.5(20 kg) (10 m/s)^2
KE= 10kg * 100 = 1000 J
The wall that is 9 ft by 10 ft is 90 square feet then add 46 square feet from the hall
90 + 46 = 136
The answer is 136 square feet
They are both similar because you just have to multiply 7 x 2 and then add the zeros. 7 x 20 is 140 and 7 x2000 is 14000
See picture for solution to your problem.