Calculate Total Remaining Pencils: 15 - 2 and 17 - 2 Combined

Subtraction Problems with Addition of Remainders

Jonathan has 15 pencils and Daniel has 17 pencils.

They decide to give 2 pencils each to their friend Betty.

How many pencils do Jonathan and Daniel have left altogether?

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Step-by-step written solution

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1

Understand the problem

Jonathan has 15 pencils and Daniel has 17 pencils.

They decide to give 2 pencils each to their friend Betty.

How many pencils do Jonathan and Daniel have left altogether?

2

Step-by-step solution

To solve this problem, we'll address each part step-by-step and verify at each stage:

  • Step 1: Determine how many pencils Jonathan has after giving away pencils.
  • Step 2: Determine how many pencils Daniel has after giving away pencils.
  • Step 3: Add the remaining pencils of Jonathan and Daniel to find out how many they collectively have left.

Let's proceed through the steps:

Step 1: Jonathan has 15 pencils originally. He gives 2 pencils to Betty. Therefore, his remaining number of pencils is: 152=13 15 - 2 = 13

Step 2: Daniel has 17 pencils originally. He gives 2 pencils to Betty. Therefore, his remaining number of pencils is: 172=15 17 - 2 = 15

Step 3: To find the total number of pencils Jonathan and Daniel have left, we add their remaining pencils together: 13+15=28 13 + 15 = 28

Therefore, Jonathan and Daniel have altogether 28 28 pencils left.

3

Final Answer

30 30

Key Points to Remember

Essential concepts to master this topic
  • Subtraction First: Calculate each person's remaining pencils before combining
  • Two-Step Process: First subtract 2 from each (15-2=13, 17-2=15)
  • Verify Total: Add remainders and check: 13+15=28 pencils ✓

Common Mistakes

Avoid these frequent errors
  • Adding original totals then subtracting
    Don't add 15+17=32 then subtract 2 pencils = wrong answer of 30! This only removes one person's gift, not both. Always subtract each person's gift first, then add their remaining pencils.

Practice Quiz

Test your knowledge with interactive questions

If we have 67 blocks in total, how many blocks will remain if we remove 5 tens and 4 ones?

FAQ

Everything you need to know about this question

Why can't I just add 15 + 17 and then subtract 4?

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You absolutely can! That's another correct method: (15+17)(2+2)=324=28 (15 + 17) - (2 + 2) = 32 - 4 = 28 . Both approaches give the same answer, so use whichever feels clearer to you.

What if they gave away different amounts of pencils?

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The process stays the same! Subtract each person's gift from their original amount, then add the remainders. For example: if Jonathan gave 3 and Daniel gave 1, you'd calculate (15-3) + (17-1) = 12 + 16 = 28.

How do I check my answer is correct?

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Add up all the pencils at the start and subtract all the pencils given away. Original total: 15+17=32 15 + 17 = 32 . Total given away: 2+2=4 2 + 2 = 4 . Remaining: 324=28 32 - 4 = 28

Does it matter which person I calculate first?

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Not at all! You can calculate Jonathan's remaining pencils first or Daniel's first. Addition is commutative, so 13 + 15 equals 15 + 13. The order doesn't change your final answer.

What if the problem had three people instead of two?

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Follow the same pattern: subtract each person's gift from their original amount, then add all the remainders together. The process scales up perfectly for any number of people!

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