Solve the Equation: Finding the Missing Number in 15 - □ = 9

Subtraction with Two-Jump Strategy

Solve the subtraction exercise,

using two jumps on the number line below:

15=9 15-\Box=9

999151515

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Step-by-step written solution

Follow each step carefully to understand the complete solution
1

Understand the problem

Solve the subtraction exercise,

using two jumps on the number line below:

15=9 15-\Box=9

999151515

2

Step-by-step solution

To solve the problem 15=9 15 - \Box = 9 using two jumps on a number line, we need to break down this subtraction into simpler parts.

If we think of the subtraction using two jumps, one effective strategy is:

  • First, subtract 5 from 15 to reach the intermediate round number, 10: 155=10 15 - 5 = 10 .
  • Second, subtract from the intermediate number, 10, to reach the target, 9: 101=9 10 - 1 = 9 .

Adding both jumps together, 5+1=6 5 + 1 = 6 . Thus, the missing number in the original expression is 6 6 .

The final solution to the problem is =6 \Box = 6 .

3

Final Answer

6 6

Key Points to Remember

Essential concepts to master this topic
  • Strategy: Break subtraction into two smaller jumps using round numbers
  • Method: First jump 15 - 5 = 10, second jump 10 - 1 = 9
  • Check: Add both jumps together: 5 + 1 = 6, verify 15 - 6 = 9 ✓

Common Mistakes

Avoid these frequent errors
  • Doing subtraction in one big jump without strategy
    Don't try to find 15 - □ = 9 by guessing = wrong answers! This makes mental math harder and leads to calculation errors. Always break down subtraction using round numbers like 10 as stepping stones.

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 do I need to use two jumps instead of one?

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Using two jumps makes mental math easier! By going to a round number like 10 first, you avoid difficult calculations and reduce mistakes.

What if I choose different jumps than 5 and 1?

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That's okay! You could jump 3 + 3 or 4 + 2. As long as your jumps add up to 6, you'll get the right answer.

How do I know which round number to use as my middle step?

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Look for the nearest round number (like 10) between your starting number (15) and ending number (9). This makes both jumps easier to calculate.

What if my answer doesn't work when I check it?

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Go back and double-check your jumps! Make sure each jump calculation is correct, then add them together. Remember: 156=9 15 - 6 = 9 should be true.

Can I use this method for other subtraction problems?

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Absolutely! The two-jump strategy works great for any subtraction. Just find a convenient round number to use as your stepping stone.

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