Skip Counting by 5s - First Grade Mathematics

Have you ever held up your hand and looked at your fingers? You have five fingers on one hand! If you hold up both hands, you have ten fingers. Because our hands naturally group into fives, skip counting by 5s is one of the most natural, rhythmic, and useful math tools you will ever learn. You will use skip counting by 5s to count nickels in money, to tell minutes on a clock, and to tally up scores in games. In this chapter, you will master skip counting by 5s up to 100 and discover the simple alternating pattern that makes it so easy.

The Skip Counting Pattern by 5s

When you count by 5s, you add five units with every single hop.

Hopping by 5s to 50:
[ 5 ] -> [ 10 ] -> [ 15 ] -> [ 20 ] -> [ 25 ]
[ 30 ] -> [ 35 ] -> [ 40 ] -> [ 45 ] -> [ 50 ]

The Alternating Endings: 5 and 0

Look closely at the last digit of every number when you count by 5s: 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100. The ones digit alternates back and forth forever: 5, 0, 5, 0, 5, 0! If a number does not end in a 5 or a 0, it cannot belong to the counting by 5s family.

High-Five Hands

Imagine a line of your friends giving you high-fives. Friend 1 gives 5 fingers: total is 5. Friend 2 gives 5 fingers: total is 10. Friend 3 gives 5 fingers: total is 15. Friend 4 gives 5 fingers: total is 20. With each high-five, you add 5 more fingers!

Spotting 5s on the Hundreds Chart

When you shade the numbers you land on when counting by 5s on a 100 chart, a stunning visual pattern appears.

The Two Columns of 5s on a 100 Chart:
Row 1:   .  .  .  . [ 5]  .  .  .  . [10]
Row 2:   .  .  .  . [15]  .  .  .  . [20]
Row 3:   .  .  .  . [25]  .  .  .  . [30]
Row 4:   .  .  .  . [35]  .  .  .  . [40]
Row 5:   .  .  .  . [45]  .  .  .  . [50]

The Two Straight Columns

All numbers ending in 5 form one straight vertical column down the middle of the chart. All numbers ending in 0 form a second straight vertical column down the right side of the chart. Only two columns on the entire chart are touched!

Counting Nickels and Tally Marks

Counting by 5s appears everywhere in practical daily math.

Counting 4 Nickels (Each Nickel = 5 Cents):
  (5c)       (5c)       (5c)       (5c)
   |          |          |          |
  5c        10c        15c        20c
Total: 4 nickels = 20 cents!

Counting Tally Bundles:
  ||||/     ||||/     ||||/
    5         10        15
Total: 3 bundles = 15 tallies!

Tally Bundles

When people make tally marks, they draw four straight sticks and cross the fifth stick diagonally across them to make a closed gate of five. You can count bundles of tallies in seconds simply by skip counting by 5s!

Practice Exercises

Exercise 1: Recite and write down the sequence of skip counting by 5s starting at 5 and ending at 50.

Exercise 2: Fill in the missing numbers: 15, 20, , 30, , 40, 45, __.

Exercise 3: You have 6 nickels in your piggy bank. Each nickel is worth 5 cents. Use skip counting by 5s to find how much money you have in all.

Exercise 4: Look at these three numbers: 35, 42, 50. Which number does NOT belong in the skip counting by 5s sequence, and why?

Solutions and Explanations

Solution to Exercise 1: The sequence counting by 5s from 5 to 50 is: 5, 10, 15, 20, 25, 30, 35, 40, 45, 50.

Solution to Exercise 2: The missing numbers are 25, 35, and 50. The complete sequence is 15, 20, 25, 30, 35, 40, 45, 50.

Solution to Exercise 3: Counting 6 nickels by 5s: 5, 10, 15, 20, 25, 30. You have 30 cents in all.

Solution to Exercise 4: The number 42 does not belong in the sequence. Every number when counting by 5s must end in either a 5 or a 0. The number 42 ends in 2.