Ratios Flashcards
The ratios of professors to administrators is 3 to 4. If the number of professors increased by 5 and the number of administrators increased by 5, what is the ratio of these two new quantities?
It is tempting to add 5 to both 3 and 4 to get a new ratio of 8/9 however, 3 and 4 is the ratio not the actual number of professors and administrators so it is impossible to know what the actual numbers are and as a result the answer cannot be determined.
In a zoo there are 25% of the animals are reptiles. If there are 80% as many birds as reptiles and the zoo only contains reptiles, birds and mammals, then what is the ratio of reptiles to birds to mammals?
First, if there are 100 animals in the zoo, how many birds are there?
25 reptiles * .8 = 20 birds
and 55 mammals
ratio is 5:4:11
A crate of fruits contains only apples, peaches and grapes. If the ratio of apples to peaches is 10 to 12 and the ratio of grapes to apples is 10 to 25, how many more peaches than grapes does the crate of fruit contain if there are 78 fruits in the crate?
30 24 18 12 8
remember, you can write ratios as fractions (basically)
so apples to peaches reduced to 5/6
and grapes to apples reduces to 2/5
from here set up a ratio box
the difference is 36 - 12 which equals 24
Initially, a certain school has 400% more students than professors. 20 students transfer from the school. How many students are left at the school if there were initially 600 total students and professors at the school?
500 480 460 400 200
answer = D, 480
plug in
Since there were initially 600 total students and professors start with choice C and add the 20 students that were transferred to get 460 + 20 = 480 and do 600 - 480 = 120 which would equal the number of professors, then 400% of 120 = 120 * 4 which equals 480 then you have to add the amount of professors which would be 480 + 120 = 600 , which equals the number of students, NOT students and professors
if I have 400% as much money as you, I have what you have plus 400% of what you have so in this case 120 + 480 = 600 student which can’t be true because there are 600 total students and professors
next try a smaller number since that one resulted in something too big
answer = B, 480.
When you see the totals of things that is a clue to do what??
SET UP A PROPORTION
get the sum of the things and set up a proportion
