Grade 1 · Place Value · MAT-01-PV-006
Find 10 More and 10 Less
Find 10 more or 10 less than a two-digit number without counting by ones.
Learning objectives
What you should be able to do
- Find 10 more or 10 less than a two-digit number without counting by ones.
- Explain that changing by 10 changes the tens while keeping the ones digit the same in typical two-digit cases.
- Use a 120 chart and base-ten blocks to verify the pattern.
Prerequisite check
Make sure the foundation is ready.
Checks place-value structure.
Checks chart/navigation readiness.
Learn
Build the idea from meaning, not memorization.
Ten more adds one ten
Ten more than 34 is 44. The four ones remain four ones; the number of tens increases from three to four.
Ten less removes one ten
Ten less than 67 is 57. The seven ones stay the same; six tens become five tens.
A 120 chart shows vertical patterns
On a typical ten-column number chart, moving down one row adds ten and moving up one row subtracts ten. The ones digit remains in the same column.
Use place value instead of counting ten single steps
Counting 35,36,37... can work, but place-value reasoning is faster and more general: add or remove one tens rod.
Interactive math lab
Change it. See what stays true.
Base-Ten Lab
Change hundreds, tens, and ones and watch the total rebuild from place value.
- add ten rod
- remove ten rod
- chart row hop
- cross 100
Worked examples
Twenty different ways to see the concept work.
10 more than 23
332 tens become 3 tens; 3 ones stay.
10 more than 34
44Add one ten.
10 more than 56
66Ones digit stays 6.
10 more than 78
88Add one group of ten.
10 more than 89
998 tens become 9 tens.
10 more than 90
1009 tens plus one ten = 10 tens.
10 less than 33
23Remove one ten.
10 less than 44
34Ones stay 4.
10 less than 66
56Remove one tens rod.
10 less than 88
788 tens become 7 tens.
10 less than 99
899 tens become 8 tens.
10 less than 100
90Ten tens minus one ten = nine tens.
What stays same in 47→57?
7 onesOnly tens increase.
What changes in 47→37?
Tens decrease by 1Ones remain seven.
Is 52→62 a change of 10?
YesOne extra ten.
Is 52→53 a change of 10?
NoThat is one more.
Chart: move one row down from 71.
81Down adds ten on a ten-column chart.
Chart: move one row up from 84.
74Up subtracts ten.
Why is 10 more than 95 equal 105?
9 tens become 10 tens while 5 ones stayCrossing 100 uses same place-value idea.
Explain without counting: 10 less than 63.
Remove one ten: 6 tens→5 tens, 3 ones stay; 53Place-value reasoning.
Practice
Guided practice with hints
0110 more than 27.
Hint: Add one ten.
Answer: 37
0210 less than 72.
Hint: Remove one ten.
Answer: 62
03What digit stays same in 48→58?
Hint: Ones digit.
Answer: 8
0410 more than 94.
Hint: Cross 100 if needed.
Answer: 104
0510 less than 101.
Hint: Remove one ten.
Answer: 91
06Why can you skip counting by ones?
Hint: You are changing an entire ten.
Answer: Place value.
Practice
Independent practice
0110 more than 31
Answer: 41
0210 more than 68
Answer: 78
0310 more than 97
Answer: 107
0410 less than 45
Answer: 35
0510 less than 80
Answer: 70
0610 less than 110
Answer: 100
07What usually stays same?
Answer: Ones digit
08What changes by one?
Answer: Number of tens
Common mistakes
Learn to catch the error, not just the answer.
Add a tens rod, not a single one.
Track place values; usually the ones remain unchanged.
Continue using tens: 90+10=100, 95+10=105.
Applications & challenge
Use the idea beyond a single exercise.
Applications
- Adjust a count after adding or removing a bundle of 10 items.
- Use a number chart to reason about values one row apart.
Challenge problems
10 more than 119
129, beyond the Grade 1 chart but same rule
Why do numbers 34 and 44 have same ones digit?
Adding ten changes tens, not ones.
What is 20 more than 53 using the same idea?
73, add two tens.
What is 30 less than 86?
56, remove three tens.
Flashcards
Retrieve it from memory.
Flashcards
Card 1 of 6
Game mode
Ten-Hop
Move by tens on a 120 chart and predict the new number before the hop.
Practice
Mastery check
0110 more than 46
Answer: 56
0210 less than 73
Answer: 63
0310 more than 96
Answer: 106
0410 less than 100
Answer: 90
05What changes in 54→64?
Answer: Tens increase by one.
06What stays same?
Answer: 4 ones
07Why not count ten single steps?
Answer: Place value lets you add/remove one ten directly.
08What is 20 more than 41?
Answer: 61
Terminology
Words to know
- ten more
- One additional group of ten.
- ten less
- One fewer group of ten.
- tens digit
- Digit showing number of tens.
- number chart
- An organized display of numbers used to see patterns.
Continue learning
Connected concepts
Curriculum references
Standards and instructional references
California Common Core State Standards for Mathematics — Grade 1 Number & Operations in Base Ten
Grade 1 place-value arithmetic and mental-ten relationships.