Subtraction By Counting Up (Frog Method)

Objectives

To remember and reinforce the Frog method of counting up when carrying out subtraction.

Resources

Abacus 4 Textbook 2 | Squared paper | Frog Method - Recap (YouTube)

Today's Lesson

Main Activity

As a mental warm up, call out a few analogue times and ask your student what their equivalents are in digital time. Then call out some digital times to be converted to analogue time.

Turn to page 48 in Abacus 4 Textbook 2.

Remind your student of how to complete subtraction calculations by adding or counting on. Watch Frog Method - Recap (YouTube) to recap Frog with smaller numbers if needed.

For the calculations on page 48, you would firstly add on as much as needed to get to the next 100, then jump in 100s to the 1000 required.

For example:

1000 – 750 =


750 + 50	= 800
800 + 200	= 1000
50 + 200	= 250

Therefore, 1000 – 750 = 250

Once your student has recalled the ‘Frog’ method of subtraction, ask them to complete the first 12 calculations on the page. Then look at the second half of the page together and draw a number line, so that your student can investigate how many times 175 can be subtracted from 1000.

Citations

[1] youtu.be [2] www.youtube.com