<u>Answer:</u>
B. He multiplied the dividend by 100 instead of 10.
<u>Step-by-step explanation:</u>
Chen had to divide by
. To make it easier to divide, he thought of multiplying both the dividend and the divisor by 10.
Chen multiplied the divisor by 10 but mistakenly multiplied the dividend by 100 instead of 10.
So his whole division problem was changed.
Therefore, the correct answer option is B. He multiplied the dividend by 100 instead of 10.