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2nd grade · Math · Unit 17 of 18

Add Up to Four Numbers

Tens with tens, ones with ones

What your child practices

Adding three or four two-digit numbers by adding tens and ones and looking for numbers that make a ten, explaining in words why these strategies work, solving two-step word problems within 100, and writing an even number as a double (8 = 4 + 4).

New York State Learning Standards learning standard: NY-2.NBT.6; NY-2.NBT.9; NY-2.OA.1b; NY-2.OA.3b · adding up to four two-digit numbers using place value, explaining why addition and subtraction strategies work, solving two-step word problems within 100, and writing an even number as a sum of two equal addends

How we explain it

Children can open this short lesson before they practice.

  1. Add the tens together, then the ones together.
  2. Look for ones that make 10, like 8 and 2.
  3. Put the tens and ones back together for the total.

Example: 23 + 18 + 32 + 14 = ? Tens: 20 + 10 + 30 + 10 = 70. Ones: 3 + 8 + 2 + 4 = 17. 70 + 17 = 87. Answer: 87

Add Up to Four Numbers in New York

In the New York State Learning Standards, this is unit 17 of 18 in 2nd grade Math, after Bar Graphs and before Lengths & Line Plots.

Gradelings describes a child's practice on this unit as Beginning, Approaching, Meeting or Exceeding (Four practice steps). That reflects practice, not a report-card mark: the teacher decides the mark.

Source: New York State Education Department (NYSED)

Sample questions

A taste of this unit. In the app, questions change every time and get easier or harder to match your child.

  1. Question 1

    Why is 14 + 40 = 54?

    • 1 ten and 4 tens make 5 tens, and the 4 ones stay the same
    • 4 ones and 4 ones make 8 ones
    • 1 ten and 4 ones make 5 tens
    • you add 4 to the ones digit

  2. Question 2

    Leo has 41 stickers, gets 21 more, then gives away 50. How many stickers now?

    • 14
    • 12
    • 1
    • 62

  3. Question 3

    Why can you add 15 + 28 + 5 as 15 + 5 + 28?

    • You can add numbers in any order and get the same total
    • Adding is the same as subtracting
    • 15 and 5 are both odd
    • The biggest number must go last

  4. Question 4

    Zoe picks 26 apples. A friend picks 22 more than Zoe. How many apples do they pick in all?

    • 74
    • 48
    • 70
    • 52

  5. Question 5

    To find 85 − 39, Ana does 85 − 40 = 45. What should she do next?

    • Add 40: 85
    • Add 1, because she took away 1 too many: 46
    • Nothing: 45 is the answer
    • Take away 1 more: 44

  6. Question 6

    Ana adds 64 + 34 + 36 by doing 64 + 36 first. Why does that help?

    • 36 is the smallest number, so it goes first
    • You must always add the last number first
    • 64 + 36 = 100, a number of tens that is easy to add to
    • The order changes the total, so this order is the right one

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