To square a number that ends in 5, Multiply the tens digit (first digit / left digit) by the next consecutive higher number (itself+1), then append (put) 25 to the end. That’s all!
Example:
o If the number is 35, 3 × 4 = 12 (first digit times next number). 1 2 _ _
o The last part of the answer is always 25: _ _ 2 5.
o So 35 × 35 = 1225
o For 65 × 65, 6 × 7 = 42 (first digit times next number): 4 2 _ _.
o The last part of the answer is always 25: _ _ 2 5.
o So 65 × 65 = 4225
See the pattern?
75 x 75 = 5625
The answer is in two parts: 56 and 25.
The last part is always 25.
The first part is the first number, 7, multiplied by the number “one more”, which is 8:
So, 7 x 8 = 56
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