Key points
- It is not always easy or necessary to give an exact value, so estimationTo arrive at a rough or approximate answer by calculating with suitable approximations for terms. can be made.
- Estimating is a way of making a calculation more manageable. For example, if you were going to buy 12 items that cost 拢28.99 each then an estimate of the total might be 拢300 (rounding both numbers to the nearest 10 is 10 lots of 拢30).
- As there isn't one set way to estimate, people might round their values in slightly different ways.
- A number can be rounded in different ways depending on its size. For example, to the nearest:
- whole number
- ten
- hundred
- thousand
Estimating Values
Estimating means making numbers simpler but keeping their value close to what it was. The result is not exact, but it gives an idea of what the total will be.
There are steps which can be followed to decide how to round a value to make it easier to deal with.
Find the most important digit in the value you have been given. This is usually referred to as the most significant figureSignificant figures are each of the digits in a value, often a measurement, that contribute to the degree of accuracy of the value..
Establish what place value column the most significant figure is positioned. Round the value to that degree of accuracyAccuracy is how close a measured value is to the actual (true) value..
Refer back to the rules of rounding to decide whether this value should be rounded up or down.
Leave it the same if the next digit is less than 5 (this is called rounding down).
But increase it by 1 if the next digit is 5 or more (this is called rounding up).
Examples
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Comparing different prices
- People often make decisions about what offer might provide the best value for money. This could be when choosing between two different sized boxes of cereal in a supermarket or deciding which mobile phone contract is offering better value for money.
- Using estimation can help people to make more informed decisions about which product or offer would represent the best value.
Examples
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Question
A shop wants to buy 78 boxes of cereal from the wholesaler. Each box costs 拢1.08. Estimate the total cost of this order.
78 rounded to the nearest ten is 80拢1.08 rounded to the nearest 拢 is 拢1
The estimated cost of the order is 80 x 拢1 = 拢80
Practise estimating
Practise estimating with this quiz.
Quiz
Real-world maths
Estimating numbers is used regularly in everyday life. It is used to make calculations more manageable.
In the video, we see how estimation can be used by a catering company to predict the amount of ingredients needed for an event:0.75 kg of tomatoes are needed for 10 people.
To estimate how much produce to buy for the full party of 70 people, we need to multiply 0.75 by 7:0.75 脳 7 = 5.25 kg
This tells us that we need at least 5.25 kg of tomatoes. The manager adds an extra 10% on to the total in case some of the tomatoes are squashed or damaged, and rounds up to 6 kg.
This is only an estimate as it is not always possible to predict exactly how many tomatoes are required.
Game - Divided Islands
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Using your maths skills, help to build bridges and bring light back to the islands in this free game from 麻豆官网首页入口 Bitesize.
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