Questions: Doubles Facts Within 10

Question 1

A student knows that 4 + 4 = 8. She needs to solve 4 + 5. How can her doubles knowledge help?

• A. She cannot use doubles — 4 + 5 is not a doubles fact, so she must count all the way from 1
• B. Since 4 + 5 is one more than 4 + 4, the answer is 8 + 1 = 9
• C. She should use 5 + 5 = 10 and then add 1 to get 11
• D. Doubles only help when both numbers are the same, so 4 + 5 cannot be solved this way

Answer: (B)

This is the 'near-doubles' strategy: 4 + 5 is just one more than the doubles fact 4 + 4 = 8, so the answer is 9. Knowing doubles is valuable not just for their own answers but as anchors for figuring out adjacent facts. Option C uses the wrong double and adds instead of subtracts, giving 11 — the wrong answer.

Question 2

Which of the following is a doubles fact?

• A. 3 + 4 = 7
• B. 2 + 3 = 5
• C. 4 + 4 = 8
• D. 5 + 6 = 11

Answer: (C)

A doubles fact requires both addends to be exactly the same number. Only 4 + 4 = 8 fits — both numbers added are 4. The other options (3+4, 2+3, 5+6) are near-doubles, where the addends differ by 1. Mixing up doubles and near-doubles is the most common misconception for this topic.

Question 3

3 + 4 is a doubles fact because both 3 and 4 are small numbers close together.

• T. True
• F. False

Answer: False

A doubles fact requires both addends to be identical — the same number added to itself. 3 + 4 has two different addends (3 and 4), so it is a near-double, not a double. Being 'close together' is not the criterion; being exactly equal is.

Question 4

Every doubles fact within 10 (1+1 through 5+5) has an even number as its answer.

• T. True
• F. False

Answer: True

1+1=2, 2+2=4, 3+3=6, 4+4=8, 5+5=10 — every answer is even. This is not a coincidence: a doubles fact creates two perfectly equal groups, and a number is even precisely when it can be split into two equal groups. Doubles and even numbers are directly connected.

Question 5

Why do doubles facts always result in even numbers?

Model answer: A doubles fact adds the same number to itself, which creates two perfectly equal groups. An even number is defined as a number that can be split into two equal groups with nothing left over. Because doubles always produce two identical groups, their sums are always even.

The connection is deeper than memorization: understanding why doubles are always even reinforces the definition of even numbers and gives students a conceptual anchor. Every even number up to 10 corresponds to a doubles fact, and every doubles answer is even.