104fE: Ratios and Percentages

Question 1

Ratio format

Answer 1

X:Y

“X” is COMPARED to “Y”. Ie. “x inches” : “y feet” on a drawing

Question 2

Rates format

Answer 2

Division format of ratios

KM/hour
$/hour

Question 3

Direct proportion solving

Answer 3

A/b = x/y
CROSS MULTIPLY to solve for “x”

Question 4

Indirect proportion solving: increase in one causes decrease in other

Answer 4

“Ratios are equal by multiplication”
X:y —> x*y

So 18 days for 5 workers; how many days for 15 workers becomes:

185=x15
(18*5)/15=x
90/15=x
6 days = x

Question 5

80 percent of x

Answer 5

.8*x

Question 6

20 is what % of 100?

Answer 6

20/100 = .2 = 20%

Question 7

100 reduced by 15% = x

Answer 7

100*.15 = 15
100 - 15 = 85 = x

OR

MULTIPLY the WHOLE by the OPPOSITE percentage of the reduction:
100*.85 = 85 = x