Jib sees a news story about a strange object. He must use his knowledge of counting in 3s to discover the object’s secret.
More resources for Autumn Block 1 Step 10.
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Discussion points for teachers
1. If I start counting from the start number and count up in 3s, how many numbers will include the digit 3 before I reach the finish number?
Discuss what the start and finishing numbers are. Discuss what number is represented by the images. Discuss counting in 3s from the starting number and how to then record how many of those numbers will have a 3 digit in them.
There are 4 numbers with a 3 between 18 and 42 when counting in 3s: 30, 33, 36 and 39.
2. Help him unlock the cube by finding the number sequence.
Discuss that the pattern shows the numbers that are part of the sequence. Discuss whether they are selecting the correct number by counting on 3 each time.
This numbers needed for the code are 24, 27, 30, 33, 36
3. Help him complete the number sequence by finding the missing numbers.
Discuss which numbers are represented by the asteroid counters. Discuss whether the sequence is ascending or descending. Discuss how they can find the missing numbers by count back 3 each time or by working from the other end and counting on 3 each time.
The missing numbers are 30 and 21.
4. How could he represent the missing numbers?
Discuss the different ways that the numbers can be represented, using words and/or numerals. Discuss how they would make the numbers if they used the asteroid counters or other representations of tens and ones. This question is open-ended for the children to explore.
The numbers could be given as 30 and 21, or thirty and twenty-one. They could also be represented using 3 tens and 2 tens, 1 ones using different manipulatives, for example the asteroid counters, place value counters or Base 10.
Optional discussion points:
Can we count in 3s from any number or is it only multiples?
National Curriculum Objectives
Mathematics Year 2: (2N1) Count in steps of 2, 3 and 5, from 0, and in tens from any number, forward or backward
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