Module 16: Percent Word Problems

Question 1

When a number is divided by a number with a power of 10, the decimal point is ______

Answer 1

moved to the left by the number of zeroes in the divisor.

5/1000 = .005

Question 2

2 strategies for solving percent word problems

Answer 2

1) Assume the unknown quantity is 100 units of something.

2) Let the unknown quantity be represented by a variable X.

Question 3

When a question asks to solve “what percent,” I will

Answer 3

translate “what percent” into x/100 and then set up an equation to solve for X

Question 4

Translate: Z is what percent of P? (2 options)

Answer 4

Z = (x/100)*P

(Z / P) * 100 = x

Question 5

Translate: P percent of Q is equal to R.

Answer 5

p/100 * q = r

Question 6

“Percent Less Than” formula

Answer 6

Final value = Initial value * (1 - “% Less Than”/100)

Question 7

“Percent Greater Than” formula

Answer 7

Final value = Initial value * (1 + “% Greater Than”/100)

Question 8

Translate: $1000 was marked up by P percent.

Answer 8

1000 (1 + P/100)

Question 9

Translate: $1000 was marked down by P percent.

Answer 9

1000 ( 1 - P/100)

Question 10

Successive Percent Change formula

Answer 10

Apply each percent decrease one at a time; separate each step with parentheses. Multiply successive steps.

Example: $100 was marked up by 20% and then another 20%.

(100 * 1.2) * 1.2

Question 11

Percent Change formula

Answer 11

(Final Value - Initial Value / Initial Value) x 100

Question 12

Set up a formula: The size of a certain population of bacteria doubles every 30 minutes for 2 hours. What is the percent change in population?

Answer 12

Call initial population X

30 min: 2x
60 min: 4x
90 min: 8x
120 min: 16x

Plug into % chg equation

 x

15x/x = 15 = 1500%