Count in 25s | Year 5 Mathematics PDF Download

How do you count in 25s?

• There are two 25s in 50 and four 25s in 100.
• Remembering this is very useful when counting in increments of 25.
• Consider this number line:
  
• Every 25-step corresponds to a larger 50-step. Within each hundred, there are four 25-steps.
• Multiples of 25 end in 25, 50, 75, or 00.
• Counting up in increments of 25 always follows this sequence.

Examples

Example 1: What are the missing numbers in this sequence?
225 → ? → 275 → 300 → ?
Sol: When counting in increments of 25, the sequence always follows: 25, 50, 75, 00.
Thus, the missing numbers are:
225 → 250 → 275 → 300 → 325

Example 2: Wigglesworth Academy has 25 children in each class. How many children are in 7 classes?
Sol: A number line could help you solve this.

The number line shows that 7 steps of 25 is 175. You could also write this as 7 lots of 25.
As a multiplication, that would be:
25 x 7 = 175
There are 175 children in 7 classes of 25 children.

Example 3: Which number in this sequence is the odd one out?
450 → 475 → 490 → 525 → 550
Sol: Remember these guidelines for counting in 25s:

• The sequence always follows the same order.
• The tens and ones digits are always either 25, 50, 75, or 00.

Now, identify the number that stands out:
It’s 490!
Its tens and ones digits are not 25, 50, 75, or 00, breaking the pattern of counting in 25s.
The next number in the sequence after 475 should be 500:
450 → 475 → 500 → 525 → 550