Year 1: Counting in tens

Method. Count on in tens from 10.

1. Start at 10. Put your finger on the starting number.
   Start: 10
2. Add 10 each time. Change the tens. The ones stay at 0.
   20, 30, 40
3. Write the next 3 numbers.
   20, 30, 40

Check. 10 + 10 = 20. ✓

Watch out. Do not write the starting number again. Start with the next one.

Method. Count back in tens from 90.

1. Start at 90. Put your finger on the starting number.
   Start: 90
2. Take away 10 each time. Change the tens. The ones stay at 0.
   80, 70, 60
3. Write the next 3 numbers.
   80, 70, 60

Check. 90 − 10 = 80. ✓

Watch out. Do not write the starting number again. Start with the next one.

Method. 10 more means one row down on the 100 square. Only the tens change.

1. Find 20. 20 is 2 tens and 0 ones.
   20 = 2 tens and 0 ones
2. Change the tens. Add one ten. The ones stay the same.
   3 tens and 0 ones
3. Write the answer.
   30

Check. 20 + 10 = 30. ✓

Watch out. Only the tens change. 20 becomes 30, not 21.

Method. 10 less means one row up on the 100 square. Only the tens change.

1. Find 70. 70 is 7 tens and 0 ones.
   70 = 7 tens and 0 ones
2. Change the tens. Take away one ten. The ones stay the same.
   6 tens and 0 ones
3. Write the answer.
   60

Check. 70 − 10 = 60. ✓

Watch out. Only the tens change. 70 becomes 60, not 69.

Method. 10 more means one row down on the 100 square. Only the tens change.

1. Find 35. 35 is 3 tens and 5 ones.
   35 = 3 tens and 5 ones
2. Change the tens. Add one ten. The ones stay the same.
   4 tens and 5 ones
3. Write the answer.
   45

Check. 35 + 10 = 45. ✓

Watch out. Only the tens change. 35 becomes 45, not 36.

Method. 10 less means one row up on the 100 square. Only the tens change.

1. Find 58. 58 is 5 tens and 8 ones.
   58 = 5 tens and 8 ones
2. Change the tens. Take away one ten. The ones stay the same.
   4 tens and 8 ones
3. Write the answer.
   48

Check. 58 − 10 = 48. ✓

Watch out. Only the tens change. 58 becomes 48, not 57.

Method. Each number is 10 more than the one before it.

1. Look at the numbers around each gap. The numbers go up or down by the same amount each time.
   40, 50, ?, 70, ?, 90
2. Work out each missing number. Use the number before the gap, and add 10.
   Gap 3: 50 + 10 = 60
   Gap 5: 70 + 10 = 80
3. Write the missing numbers.
   60, 80

Check. Read the whole line again. Every number is 10 more than the one before. ✓

Watch out. Check the numbers after the gap too. They should still go on by the same amount.

Method. Use the numbers above and below each empty box. Going down one row adds 10.

1. Look above and below each empty box. The number above is 10 less. The number below is 10 more.
   30: 20 above, 40 below; 70: 60 above, 80 below
2. Work out each missing number. The empty box is 10 more than the number above it.
   20 + 10 = 30
   60 + 10 = 70
3. Write the missing numbers.
   30, 70

Check. Check it: the number below each box is 10 more than the box. ✓

Watch out. Look up or down the column. Do not guess from the numbers next to the box.

Method. 10 more means one row down on the 100 square. Only the tens change.

1. Find 45. 45 is 4 tens and 5 ones.
   45 = 4 tens and 5 ones
2. Change the tens. Add one ten. The ones stay the same.
   5 tens and 5 ones
3. Write the answer.
   55

Check. 45 + 10 = 55. ✓

Watch out. Only the tens change. 45 becomes 55, not 46.

Method. Each pack has 10 things. Count the tens to find the total.

1. Count the packs: 3. Each pack has 10 in it.
   3 packs of 10
2. Count in tens, one ten for each pack. Add 10 for every pack you count.
   10, 20, 30
3. Write the total.
   30

Check. Count in tens to check: the last number you say is 30. ✓

Watch out. Count in tens, not in ones. Each pack is one ten.

Method. Count in tens. Each number is 10 more than the one before.

1. Start at 30. Put your finger on the first ten.
   Start: 30
2. Jump on one ten each time. Change only the tens. The ones stay at 0.
   30, 40, 50
3. Write the numbers.
   30, 40, 50

Check. Count back in tens from 50 to 30 to check. ✓

Watch out. Change the tens, not the ones. When you count in tens, the ones digit is always 0.

Method. Look at the numbers in the right-hand column of the 100 square.

1. Look at the numbers in the column. These are the numbers that end a row.
   10, 20, 30, 40, 50 and so on
2. Look at the ones digit. Every one of them has 0 ones.
   Ones digit: 0 for every number
3. Write the answer.
   They all end in 0.

Check. 10, 20 and 30 all have 0 ones, so the ones digit is 0. ✓

Watch out. A number that ends in 0 is a ten. The 0 is the ones digit.