THE BEST ANSWER IS C. ANSWERS A AND E ARE DISQUALIFIED IMMEDIATELY...

21. - PROBLEMS PRACTICE PHẦN 10 PPSX
PROBLEMS PRACTICE PHẦN 10 PPSX
21. The best answer is C. Answers A and E are disqualified immediately because those are even numbers that cannot be divided into two equal odd numbers. 22 is 11 + 11 but 11 x 11 is bigger than 121, the same idea with 14, therefore the answer is 18. 18 = 9 + 9. 9 x 9 = 81.