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 again 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 49 in Abacus 4 Textbook 2.

Watch the 'Frog method within 10,000' video.

Using the Frog method, ask your student to copy and complete the calculations on the page. Point out that the size of the numbers should not put them off. You simply count on to the next 100, then jump in 100s to the thousand required.

If the number to be subtracted is greater than 1000, just imagine the frog jumping to those thousands.

For example:

7000 – 3465 =

3465 + 35 =3500

Then jump **+**500 to 4000 and jump **+**3000 to 7000

35 + 500 +3000 = 3535

Therefore, 7000 – 3456 = 3535

Drawing a number line to show the jumps will always be helpful to your student.

Ask your student to copy and complete the calculations on the page.

Citations

[1] youtu.be