Q13

Each tri-cycle has 3 wheels (tri means three) and each car has 4 wheels (though I have seen cars with 3 wheels before).

There are 11 times as many tri-cycles as cars.

This means that for every one car, we group 11 tri-cycles together. This is called one group.

11 tri-cycles have 33 wheels in total, so 11 tri-cycles and 1 car have 37 wheels in total. One group has a total of 37 wheels.

Since there are 73260 wheels altogether, number of groups
= 73260 / 37
= 1980

So there are 1980 groups altogether. Remember that each group has one car and 11 tri-cycles.

Number of tri-cycles
= 11 x 1980
= 21780

Q14

Each duck lays 2 eggs while each chicken lays 1 egg. So each duck lays twice as many eggs as each chicken.

Because all the ducks lay twice as many eggs as the chicken, there must have been the same number of ducks and chickens.

So, we take one duck and one chicken as one group.

Number of eggs laid by 1 group
= 2 + 1
= 3

Number of groups
= 300 / 3
= 100

So there are 100 groups altogether. This consists of 100 ducks and 100 chickens.

Number of eggs the chickens laid
= 100 x 1
= 100

Q15

Let one group contain 7 adults and 4 children.

Total cost of admission for one group
= 7 x 10 + 4 x 5
= 70 + 20
= 90

So each group pays $90.

Number of groups
= $2340 / $90
= 26

So there are 26 groups, each containing 7 adults and 4 children.

Number of children altogether
= 26 x 4
= 104