We've looked at the order of operations in Maths in Order. We can now use this process to solve problems that may involve things like money, weight and distance.

Examples

question 1

Evaluate: A jug holds $0.75$0.75l of juice. If I have $3$3 jugs, how many $250$250ml glasses can I fill?

Think: I want both units of capacity to be the same, so I am going to convert $0.75$0.75l to $750$750ml by multiplying it by $1000$1000.

Do: $750\times3=2250$750×3=2250ml

$2250\div250=9$2250÷250=9

That means I can fill $9$9 glasses.

question 2

Evaluate: What is the difference between $187$187 and the product of $15$15 and $3$3?

Think: How do I write this as an equation so that the order of operations is correct?

Do:

$187-\left(15\times3\right)$187−(15×3)	$=$=	$187-45$187−45
	$=$=	$142$142

Question 3

There were $139$139 sharks in Charon Bay last year. This year the population has decreased to $92$92 sharks.

How much of the shark population in Charon Bay was lost in the last year?

Question 4

I want to make $4$4 biscuits with $15$15 chocolate chips in each of them. How many chocolate chips do I need to use in total?

Question 5

On a certain island a species of hawk sustains itself by eating the local rabbits.

In the first survey of animals on the island, there were found to be $3$3 rabbits for every hawk. The latest survey shows that this is still the case, but that the rabbit population has grown to $153$153 individuals. How many hawks does the island now support?

Problem solving with mixed operations