Estimate with Whole Numbers

Sometimes in everyday life, it is appropriate to use estimation when talking about numbers.

 

 

We may want to calculate an approximate answer to a problem quickly, where we don't need an exact answer.

 

We can use rounding to help us estimate a solution. 

Rounding makes the numbers easier to calculate with, and so can often be done mentally. 

Example:

A shop is selling packs of biscuits for £2.17 each. I have £9 and wonder if I have enough money to buy 4 packs. 

 

 

I can round £2.17 up to £2.20, and then do 2.20 x 4 = £8.80

I rounded up, so I know it'll cost me less than £8.80, so I'll definitely have enough. 

 

Example:

 

 

In my pizza restaurant, I make pizzas that I cut into 10 slices. 

One day, I have 146 people booked into the restaurant. I know on average that people order 3 slices of pizza. 

How many pizzas will I need to make to feed everyone?

I can round 146 to 150.

Then I would do 150 x 3 = 450.

I need to make 450 slices of pizza.

450 ÷ 10 = 45. 

I should make around 45 pizzas.

 

 

Let's do some more estimation practice!