Multiple choice general knowledge math & puzzles 10,40,90,61,? what is next number? 70 91 34 52 Reveal answer Fill a bubble to check yourself D Correct answer Explanation The sequence is based on the squares of numbers 1-5 with their digits reversed: 01^2=01 (10), 02^2=04 (40), 03^2=09 (90), 04^2=16 (61). The next is 05^2=25, which reversed is 52.