What is Adding to Make 15?

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Grade Level:

Pre-School – Class 2

All domains without exception

Definition

What is it?

Adding to Make 15 means finding two or more numbers that, when put together, give you a total of 15. It's like collecting items until you have exactly 15 of them.

Simple Example

Quick Example

Imagine you have 10 cricket balls. How many more balls do you need to have a total of 15 balls? You need to add 5 more balls (10 + 5 = 15).

Worked Example

Step-by-Step

Let's say you have 7 laddoos and your friend gives you some more. Now you have a total of 15 laddoos. How many laddoos did your friend give you?
1. Start with the total number we want: 15 laddoos.
2. We already have: 7 laddoos.
3. We need to find the missing number that, when added to 7, makes 15.
4. You can count up from 7 to 15: 8, 9, 10, 11, 12, 13, 14, 15. That's 8 counts.
5. So, the missing number is 8.
6. Check: 7 + 8 = 15.
Your friend gave you 8 laddoos.

Why It Matters

Understanding how numbers combine to make a total is fundamental for all mathematics. It's crucial for managing money, like calculating change at a shop, or even for engineers designing structures where parts must add up to a specific length. This skill is useful for anyone from a shopkeeper to a scientist.

Common Mistakes

MISTAKE: Confusing addition with subtraction when finding the missing number. Forgetting that we are looking for a number to 'add on'. | CORRECTION: Always remember the 'sum' or 'total' is what you are aiming for. If you have a part and the total, you add the missing part to what you have to reach the total.

MISTAKE: Counting incorrectly when using fingers or mental math, especially missing a number or double-counting. For example, counting from 7 to 15 as 7, 8, 9, 10, 11, 12, 13, 14 (missing 15). | CORRECTION: Start counting from the number AFTER the one you have, and stop exactly at the target number. For 7 to 15, start at 8 and count until 15.

MISTAKE: Not realizing that different pairs of numbers can add up to 15 (e.g., 10+5 and 9+6). | CORRECTION: Understand that there can be multiple combinations to reach a target sum. The question usually asks for *a* number, or a specific scenario will narrow it down.

Practice Questions

Try It Yourself

QUESTION: You have 8 rupees. How many more rupees do you need to buy a snack that costs 15 rupees? | ANSWER: 7 rupees

QUESTION: A bus has 6 passengers. At the next stop, some more passengers get on. Now there are 15 passengers in total. How many passengers got on at the stop? | ANSWER: 9 passengers

QUESTION: Your mobile data pack has 15 GB for the month. You have already used 5 GB for online classes and 3 GB for watching videos. How much data do you have left? | ANSWER: 7 GB

MCQ

Quick Quiz

Which pair of numbers adds up to 15?

6 and 8

7 and 9

10 and 5

11 and 3

The Correct Answer Is:

10 + 5 equals 15. Options A (6+8=14), B (7+9=16), and D (11+3=14) do not sum to 15.

Real World Connection

In the Real World

When you go to a local kirana store in India, you often need to quickly calculate how much more money you need if you have less than the total cost. For example, if a packet of biscuits costs 15 rupees and you only have a 10-rupee note, you instantly know you need 5 more rupees to complete the purchase.

Key Vocabulary

Key Terms

ADDITION: The process of combining two or more numbers to find their total | SUM: The result of adding two or more numbers together | TOTAL: The final amount when everything is counted or added | NUMBER BOND: A pair of numbers that add up to a specific total

What's Next

What to Learn Next

Once you're good at making 15, you can try 'Adding to Make 20' and then 'Adding to Make 100'. These concepts build on the same idea but with larger numbers, which is very useful for more complex math problems and everyday calculations.