Working with Proportion Flashcards

All 6 cards in this deck

What are the steps to scale a recipe using the unitary method?
e.g. a recipe for 4 people, needed for 6 people

1. Divide each amount by the number given: $\div 4$ gives the amount for 1 person
2. Multiply by the number wanted: $\times 6$
3. Equivalent to multiplying every amount by $1.5$

What does a map scale of $1:25\,000$ mean?

1 unit on the map represents $25\,000$ of the same unit in real life.
e.g. 1 cm on the map is $25\,000$ cm $= 250$ m

True or false? To find a real distance from a distance measured on a map you divide by the scale factor.

False. You multiply the map distance by the scale factor; you divide when going from real distance to map distance.

How do you find the scale of a scale drawing?
e.g. a $2$ cm line on the drawing represents $10$ m in real life

Convert both to the same unit, then divide the real length by the drawing length.
$1000 \div 2 = 500$, so the scale is $1:500$

How do you find the amount of one ingredient in a mixture from the amount of the other?
e.g. red : yellow paint $= 2:3$ and $10$ litres of red is used

Find the value of one part, then multiply by the other number of parts.
$10 \div 2 = 5$ litres per part, so yellow $= 3 \times 5 = 15$ litres

How do you find a ratio from an equation linking two letters?
e.g. $5c + d = c + 4d$, find $c:d$

Rearrange so one letter is a multiple of the other, then read off the ratio.
$4c = 3d$, so $c:d = 3:4$