The way I know is because I memorized every square up to 33.
BUT that's probably not helpful to you.
Remember that every perfect square has an odd number of factors. I'm not going to list them all out, but the factors of 35 are 1, 5, 7, and 35, giving it an even number of factors. All the rest have an odd number of factors because of the property of a perfect square: a number times itself gives a perfect square, but that number only counts as 1 factor.
You have to divide the fractions so it 3/4÷1/10 then you can do keep change flip so the new equation is 3/4×10/1 or 3/4×10 then cross simply then get 3/2×5/1 to get 15/2 then use division to get 7 1/2
