Multiplication and addition or subtraction of whole numbers

There are 6 boats, each ferrying 21 people and 2 boats each ferrying 15 people across a river. Find the total number of people being ferried across the river in the boats.

Solution

Step 1:

Each of the six boats are ferrying 21 people each.

To find the number of people ferried by these 6 boats, we need to multiply.

So the number of people ferried by these boats

= 6 × 21 = 126.

Step 2:

Similarly, the number of people ferried by the 2 boats each carrying 15 people

= 2 × 15 = 30.

Step 3:

So the total number of people being ferried across the river by the

6 + 2 = 8 boats = 126 + 30 = 156

In a theatre there are 25 rows each having 20 seats. If the number of seats in a row are increased by 4, what is the total number of seats in the theatre now?

Solution

Step 1:

The number of seats in a row = 20

The number of seats in a row after increase

= 20 + 4 = 24

Step 2:

The number of rows = 25

Step 3:

So the total number of seats in the theatre now, i.e., after increase in seats in each row

= 25 × 24 = 600