Mental Math Within 20

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Answer Key & Explanations

Mental Math Within 20 · Grade 2 · Worksheet 3

1. 35 + 47 = ? Answer: 82 Solution: Start with 35 + 47 Break 47 into 45 + 2 to make adding to 35 easier First add 35 + 45 = 80 Then add the remaining 2: 80 + 2 = 82 The answer is 82
   Full step-by-step solution

   Step 1: Start with 35 + 47 Step 2: Break 47 into 45 + 2 to make adding to 35 easier Step 3: First add 35 + 45 = 80 Step 4: Then add the remaining 2: 80 + 2 = 82 Step 5: The answer is 82

2. A rectangular garden has 7 rows of flowers. Each row has 8 flowers. How many flowers are there in total? Answer: 56 Solution: There are 7 rows of flowers. Each row has 8 flowers. To find the total, multiply the number of rows by the number of flowers in each row: 7 × 8 7 × 8 = 56 There are 56 flowers in total.
   Full step-by-step solution

   Step 1: There are 7 rows of flowers. Step 2: Each row has 8 flowers. Step 3: To find the total, multiply the number of rows by the number of flowers in each row: 7 × 8 Step 4: 7 × 8 = 56 Step 5: There are 56 flowers in total.

3. A baker had 75 cookies in the morning. She baked 24 more cookies in the afternoon. How many cookies does she have now? Answer: 99 Solution: Start with the 75 cookies from the morning Add the 24 cookies baked in the afternoon Add the ones place: 5 + 4 = 9 Add the tens place: 70 + 20 = 90 Combine the results: 90 + 9 = 99 The baker now has 99 cookies.
   Full step-by-step solution

   Step 1: Start with the 75 cookies from the morning Step 2: Add the 24 cookies baked in the afternoon Step 3: Add the ones place: 5 + 4 = 9 Step 4: Add the tens place: 70 + 20 = 90 Step 5: Combine the results: 90 + 9 = 99 The baker now has 99 cookies.

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

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

5. Lily and Lily are playing a card game. Lily has 41 points. Lily needs 24 more points to win. How many points does a player need to win the game? Answer: 65 Solution: Lily has 41 points. Add the points needed: 41 + 24 = 65. A player needs 65 points to win.
   Full step-by-step solution

   Step 1: Lily has 41 points. Step 2: Add the points needed: 41 + 24 = 65. A player needs 65 points to win.