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# Column subtraction: Lesson 1: dolphins

## The Lesson

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In this exciting lesson, you will need to solve a range of subtraction word problems that feature dolphins. Try using PAWS to arrive at the right answer!

=  Picture the problem in your mind.

=  Annotate the word problem by highlighting the important information.

W =  Write down the number sentence that needs to be solved.

S  =  Solve the number sentence using an efficient strategy.

Useful prior knowledge:

• To confidently subtract a 2-digit number from a 2-digit number (with one exchange).

Did you know?

Scientists think that another reason that a spinner dolphin spins is to shake off parasites that have attached themselves to its skin.

## Use PAWS, counters and column subtraction to solve the following word problem.

A twenty-year old spinner dolphin had 176 tiny parasites on its body. After making 56 spinning leaps in the Pacific Ocean, it managed to remove a total of 57 parasites from its body.

How many parasites did the spinner dolphin have on its body after leaping this many times?