Infinity times nine!
Chat with our AI personalities
99 (= 11 x 9) is the largest multiple of 11 less than 100.
9*11=99
If it's to be a multiple of 9 the its digits must sum to a multiple of 9. Squares under 225 are 196,169,144,121,100... 144 ie 12 squared (and 9 x 16) would seem to be the figure you're looking for.
There is no such number. Since if x were the largest multiple of 3 and 7 then what about 2x? 2x would be a multiple of 3 since x is a multiple of 3; 2x would be a multiple of 7 since x is a multiple of 7; and 2x is bigger than x. So x cannot be the largest.
There is no largest common multiple of any two numbers: whatever common multiple is claimed to be the largest can be increased to an even larger common multiple by adding the lowest common multiple for the numbers (which for 2 and 3 is 6).