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Mental Math Within 20

Grade 2 · Mathematics · Worksheet 1

  1. Liam has 24 stickers in his collection. His friend Emma gives him 15 more stickers for his birthday. How many stickers does Liam have now? Answer: ______________
  2. Lily has 47 crayons in her art box. Her teacher gives her 28 more crayons for a special project. How many crayons does Lily have now? Answer: ______________
  3. A rectangle has 4 rows of stickers with 6 stickers in each row. How many stickers are there in total?
    Answer: ______________
  4. Nikau is collecting leaves for a school project. Nikau found 44 leaves on the way to school and 47 leaves in the park. How many leaves did Nikau find in total? Answer: ______________
  5. Noa drew a number path that goes from 0 to 100. He jumped forward 30 spaces from 0 and landed on a number. Then he jumped forward 40 more spaces. What number did Noah land on after both jumps? Answer: ______________
  6. A baker made 56 chocolate chip cookies and 38 oatmeal raisin cookies. How many cookies did the baker make in total? Answer: ______________
  7. 78 - 45 = ? Answer: ______________
  8. 83 - 47 = ? Answer: ______________
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Answer Key & Explanations

Mental Math Within 20 · Grade 2 · Worksheet 1

  1. Liam has 24 stickers in his collection. His friend Emma gives him 15 more stickers for his birthday. How many stickers does Liam have now? Answer: 39 Solution: Liam starts with 24 stickers. Emma gives him 15 more stickers. To find the total number of stickers Liam has now, we add the stickers he received to the stickers he already had.
    Full step-by-step solution

    Liam starts with 24 stickers. Emma gives him 15 more stickers. To find the total number of stickers Liam has now, we add the stickers he received to the stickers he already had. Step 1: Write the addition problem. 24 + 15 Step 2: Add the numbers. First, add the ones place: 4 + 5 = 9. Then, add the tens place: 2 + 1 = 3. Step 3: Combine the results. The total is 39. So, Liam now has 39 stickers.

  2. Lily has 47 crayons in her art box. Her teacher gives her 28 more crayons for a special project. How many crayons does Lily have now? Answer: 75 Solution: Lily starts with 47 crayons She gets 28 more crayons Add the tens: 40 + 20 = 60 Add the ones: 7 + 8 = 15 Combine the tens and ones: 60 + 15 = 75 Lily has 75 crayons now.
    Full step-by-step solution

    Step 1: Lily starts with 47 crayons Step 2: She gets 28 more crayons Step 3: Add the tens: 40 + 20 = 60 Step 4: Add the ones: 7 + 8 = 15 Step 5: Combine the tens and ones: 60 + 15 = 75 Lily has 75 crayons now.

  3. A rectangle has 4 rows of stickers with 6 stickers in each row. How many stickers are there in total? Answer: 24 Solution: The rectangle has 4 rows of stickers Each row has 6 stickers To find the total, multiply the number of rows by the number of stickers in each row: 4 × 6 4 × 6 = 24 The answer is 24.
    Full step-by-step solution

    Step 1: The rectangle has 4 rows of stickers Step 2: Each row has 6 stickers Step 3: To find the total, multiply the number of rows by the number of stickers in each row: 4 × 6 Step 4: 4 × 6 = 24 The answer is 24.

  4. Nikau is collecting leaves for a school project. Nikau found 44 leaves on the way to school and 47 leaves in the park. How many leaves did Nikau find in total? Answer: 91 Solution: Start with the leaves found on the way to school: 44 leaves. Add the leaves found in the park: 47 leaves. 44 + 47 = 91.
    Full step-by-step solution

    Step 1: Start with the leaves found on the way to school: 44 leaves. Step 2: Add the leaves found in the park: 47 leaves. Step 3: 44 + 47 = 91. Nikau found 91 leaves in total.

  5. Noa drew a number path that goes from 0 to 100. He jumped forward 30 spaces from 0 and landed on a number. Then he jumped forward 40 more spaces. What number did Noah land on after both jumps? Answer: 70 Solution: Noah starts at 0 and jumps forward 30 spaces. 0 + 30 = 30. From 30, he jumps forward 40 more spaces.
    Full step-by-step solution

    Step 1: Noah starts at 0 and jumps forward 30 spaces. 0 + 30 = 30. Step 2: From 30, he jumps forward 40 more spaces. 30 + 40 = 70. Step 3: After both jumps, Noah lands on 70. The answer is 70.

  6. A baker made 56 chocolate chip cookies and 38 oatmeal raisin cookies. How many cookies did the baker make in total? Answer: 94 Solution: The baker made 56 chocolate chip cookies and 38 oatmeal raisin cookies. Add the tens first: 50 + 30 = 80 Add the ones: 6 + 8 = 14 Combine the tens and ones: 80 + 14 = 94 The baker made 94 cookies in total.
    Full step-by-step solution

    Step 1: The baker made 56 chocolate chip cookies and 38 oatmeal raisin cookies. Step 2: Add the tens first: 50 + 30 = 80 Step 3: Add the ones: 6 + 8 = 14 Step 4: Combine the tens and ones: 80 + 14 = 94 Step 5: The baker made 94 cookies in total.

  7. 78 - 45 = ? Answer: 33 Solution: Start with 78. Subtract the tens: 70 - 40 = 30. Subtract the ones: 8 - 5 = 3.
    Full step-by-step solution

    Step 1: Start with 78. Step 2: Subtract the tens: 70 - 40 = 30. Step 3: Subtract the ones: 8 - 5 = 3. Step 4: Combine the results: 30 + 3 = 33. The answer is 33.

  8. 83 - 47 = ? Answer: 36 Solution: Start with 83 - 47. Since 3 is less than 7, we cannot subtract the ones directly. Break 83 into 70 + 13.
    Full step-by-step solution

    Step 1: Start with 83 - 47. Step 2: Since 3 is less than 7, we cannot subtract the ones directly. Break 83 into 70 + 13. Step 3: Subtract 40 from 70: 70 - 40 = 30. Step 4: Subtract 7 from 13: 13 - 7 = 6. Step 5: Combine the results: 30 + 6 = 36. The answer is 36.