Arithmetic Reasoning (KNOWLEDGE)

Distance formula

Distance = Rate × Time

Rate formula

Rate = Distance ÷ Time

Time formula

Time = Distance ÷ Rate

Work-rate (two people)

If one takes a hours and the other takes b hours, together they take (a × b) ÷ (a + b) hours

Simple interest

Interest = Principal × Rate × Time (rate as decimal)

Finding a percent of a number

Part = Percent × Whole

Finding the whole when you know the part and percent

Whole = Part ÷ Percent

Percent increase

New amount = Original × (1 + rate)

Percent decrease

New amount = Original × (1 − rate)

Finding the original after a percent change

Original = New ÷ (1 ± rate)

Ratio a:b when a = k

b = k × (b’s part ÷ a’s part)

Average

Average = Total sum ÷ Number of items

Total from average

Total = Average × Number of items

Profit

Profit = Selling price − Cost

Profit percent

Profit % = (Profit ÷ Cost) × 100%

Sale price after discount

Sale price = Original × (1 − discount rate)

Final price with sales tax

Final = Price × (1 + tax rate)

Probability of independent events both happening

Multiply the individual probabilities

Probability of one or the other (mutually exclusive)

Add the individual probabilities