Ratio and Rate
Ratio is the proportion of quantities. For example if there are three apples to six oranges, the ratio of apples to oranges in its simplest form is 1:2.
Rate is how fast the quantity of an object changes. Speed is an example of rate.
Let us try a past year Primary School Leaving Examination (PSLE) Question on Ratio and Rate.
A faster machine completes printing the same number of documents in 70 minutes while a slower machine can print the same number of documents in 100 minutes. What is the total number of documents printed by the 2 machines given that the faster machine prints 6 more documents per minute than the slower machine?
Solution
The ratio of speeds of the faster machine to slower machine is 100:70 or 10:7.
The difference in units = 10-7=3
Speed of slower machine = 2*7=14 documents per minute.
Total no of documents printed by the 2 machines = 14*100*2=2800