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Addition Patterns
Objectives
To be able to see a pattern in a continuing calculation and to be able to answer an addition using this pattern without having to work out the addition each time.
Resources
Abacus 4 Textbook 3 | Squared paper
Today's Lesson
Main Activity
Ask your student to count on in 50s from any random number for about 5 numbers.
For example:
13, 63, 113, 163, 213, 263
Then ask them to count on in 25s from a starting number for the next 5 numbers.
For example:
6, 31, 56, 81, 106, 131
Turn to page 47 in Abacus 4 Textbook 3.
Ask your student to copy the first calculation of Pattern 1 out on squared paper. Point out that the 100s barrier has not been ‘broken’. Therefore, the answer to the second part of the pattern will have no effect on the hundreds digit; it will remain the same. Discuss the fact that if we know 38 + 45 = 83 then we also know what 538 + 45 =, and what 4238 + 45 =
Therefore, it is only necessary to work out the calculation for the first part of the pattern. The remaining two answers should not need to be worked out completely.
Ask your student to copy and complete the calculations on page 47, only working out the first of each pattern.
Then, ask your student to attempt the problems mentally, before writing the calculations and answers down.