Explain how you could estimate 22% of 78 to check if your answer is reasonable

he got it

he is right. i give him an a+

What i think you could do is round the numbers you have to something reasonable, especially if you're not supposed to use a calculator. so round 22% down to 20% and then round 78 up to 80, then solve. with the estimate you should get 16, which should be close to the answer you would get if you took  22% of 78.