Puzzler This is a ten-piece subtraction puzzle.


Here is an example of a completed grid:


If you start at the bottom and look at the numbers on each line going up, you will notice that every number is the difference between the two numbers above it.


0 1 5 2 1 4 3 3 1 2


Now let’s see if you can complete a ten-piece subtraction puzzle! In order to complete the puzzler grid, start at the top row and work downwards. The ten numbers that you will need to insert correctly into the grid are below. Good luck!


4 3 3 Estimating To estimate means to guess.


When we talk about estimating an answer, we mean that we make a guess at the answer.


We never make a ‘wild guess’, though, we always make an ‘educated guess’. James and his sister Kate were picking blackberries. James collected 178 blackberries and Kate collected 159.


Estimate the difference in the number of blackberries they picked. Why did you guess that number? Discuss your estimate with your classmates and your reasons for your estimate. Did you make a ‘wild guess’ or an ‘educated guess’?


Remember: a good estimate is an estimate that is close to the real answer.


Reminder: A tip for making a good estimate is to fi rst ‘round’ each number to the nearest ten and then subtract the numbers in your head.


Let’s look at the example above:


178 – 159 = ? 178 rounds up to 180, and 159 rounds up to 160. We know 180 – 160 = 20, so 20 would be a good estimate.


Now let’s work out the answer properly and see if our estimate was close . . . 1 6


71 8


– 1 5 9 1 9


24 Our estimate of 20 is close to 19, so that was a good estimate! Subtraction 2 2 2 1 1 1 0


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