VERIFIED ANSWERS
dividing fractions - ✔✔ don't ask why, invert the second fraction and multiply
dividing mixed fractions - ✔✔ convert any mixed fraction to an improper fraction,
and divide as usual
(invert the second fraction and multiply)
percent formula - ✔✔ is/of = %/100
percent change - ✔✔ amount of change divided by original amount, times 100
(amount of change/original amount * 100)
percent increase - ✔✔ subtract old amount from new amount, divided by original
amount times 100
([new amount - old amount]/original amount * 100)
percent decrease - ✔✔ subtract new amount from old amount, divided by original
amount times 100
([original amount - new amount]/original amount * 100)
, Amount increase or decrease - ✔✔ multiply original price times % mark up, or
mark down
(original price * percent mark up or mark down)
original price equals - ✔✔ divide new price by whole amount minus % mark up,
or mark down
(new price/[whole - percent mark down or mark up])
finding ratio equivalents - ✔✔ cross multiply with given ratio and information
ratios; finding the whole when a total is given - ✔✔ convert the ratio to a fraction
by adding together the parts of the ratio, this sum is the whole and will be the
denominator to the parts to cross multiply.
(ratio 5:4 = 9; 4/9 and tot 90 is 4/9 = x/90; x = 40)
direct proportion - ✔✔ two quantities that are directly proportional will increase or
decrease in tandem. They change in the same direction. For direct proportions,
solve by cross multiplying.
inverse proportion - ✔✔ two quantities which are inversely proportional will
change in opposite directions. As one increases, the other will decrease. For