The sum of internal angles of a polygon: 180 x (n-2) n is the number of sides of the polygon.

Distance divided by time equals speed.

Distance divided by speed equals time.

Speed times time equals distance.

Area of parallelogram: base times height

Area of triangle: base times height divided by 2.

Trapezoidal area: (upper bottom+lower bottom) × height /2

Pile number: (bottom number-top number)/tolerance+1

Total number of stakes: (number of top stakes+number of bottom stakes) x number of floors /2.

Differential multiple problems:

(sum+difference) /2= larger number.

(sum and difference) /2= smaller number

Sum multiplication problem: sum/(multiply+1) = multiply 1.

One profit and one loss: (abundance+loss)/difference between two deliveries = quantity of goods delivered each time.

Appendix+Appendix = Sum

And-one addend = another addend

Factor * factor = product

Product/one factor = another factor

Negative-negative = difference

Difference+Minus = Minus

Dividend/divisor = quotient

Dividend/quotient = divisor

Divider * quotient = dividend