Maths Calculations - an another way

15 * 15   = ??

25 * 25   = ??

35 * 35   = ??

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Here is a simple way to calculate these

Just append 25 at the end

15 * 15 = (1*1)+1 append(25) == 2   25

25 * 25 = (2*2)+2 append(25) == 6   25

35 * 35 = (3*3)+3 append(25) == 12  25

45 * 45 = (4*4)+4 append(25) == 20  25

55 * 55 = (5*5)+5 append(25) == 30  25

65 * 65 = (6*6)+6 append(25) == 42  25

75 * 75 = (7*7)+7 append(25) == 56  25

85 * 85 = (8*8)+8 append(25) == 72  25