Quick mental math
Break big numbers into easy parts and the calculation gets simple.
To multiply by 10, add a zero to the end of the number.
To divide by 5, multiply by 2 and then divide by 10.
Example
24 × 15 = (24 × 10) + (24 × 5) = 240 + 120 = 360
Example
35 ÷ 5 = (35 × 2) ÷ 10 = 70 ÷ 10 = 7