Questions: Multiplication Facts: 2s, 5s, and 10s

Question 1

You know that 5 × 8 = 40. How can this help you figure out 6 × 8?

• A. It can't — 6 × 8 is a completely different fact
• B. Add one more group of 8: 40 + 8 = 48, because 6 groups is one more than 5 groups
• C. Double 40, because 6 is close to double 5
• D. Add 6 and 5 to get 11, then multiply by 8

Answer: (B)

This is the 'anchor facts' idea: 6 × 8 means six groups of 8. If five groups of 8 is 40, you need exactly one more group of 8 to reach six groups: 40 + 8 = 48. The 2s, 5s, and 10s facts serve as anchor points precisely because nearby harder facts can always be reached by adding or subtracting one group. This strategy turns memorization into a reasoning process.

Question 2

Why does multiplying any whole number by 10 always produce an answer that ends in zero?

• A. Because 10 is an even number, and even times any number ends in zero
• B. Because multiplying by 10 shifts every digit one place to the left in our place-value system, leaving the ones place empty
• C. It is a coincidence that happens to be useful for the multiplication table
• D. Because 10 has two digits, so the answer always gains an extra digit on the right

Answer: (B)

Multiplying by 10 is a place-value shift. In our base-10 system, each place is worth 10 times the place to its right. Multiplying by 10 moves every digit one step to the left — ones become tens, tens become hundreds — and the ones place is now empty, so it reads as 0. 6 × 10 = 60: the 6 has moved from the ones place to the tens place. This insight connects multiplication directly to place value and explains why the pattern is perfectly reliable.

Question 3

Multiplying 2 × 9 gives the same result as adding 9 + 9.

• T. True
• F. False

Answer: True

Multiplying by 2 means 'two groups of,' which is exactly the same as adding the number to itself. 2 × 9 = two groups of 9 = 9 + 9 = 18. This connection to addition doubles is what makes the 2s facts easiest to learn — every 2s fact is already a known double: 2 × 3 = 3 + 3 = 6, 2 × 7 = 7 + 7 = 14.

Question 4

The 2s, 5s, and 10s facts are called 'anchor facts' because they are the primary multiplication facts students ever need to know.

• T. True
• F. False

Answer: False

Anchor facts are called that because you use them to derive other, harder facts — not because they're sufficient on their own. Knowing 5 × 8 = 40 helps you find 6 × 8 (add one group of 8), and knowing 2 × 7 = 14 helps you find 4 × 7 (double it). The 2s, 5s, and 10s are stepping stones toward the full multiplication table, not the complete destination.

Question 5

How is multiplying by 2 connected to skip counting, and why does this connection help with the 2s facts?

Model answer: Skip counting by 2 (2, 4, 6, 8, 10, ...) produces the 2s multiplication table in order. The nth number in the sequence is 2 × n — so the 4th stop, 8, is the answer to 2 × 4. The connection helps because skip counting is already familiar: you can reconstruct any 2s fact by counting up by 2s to the nth stop, even before you have it memorized.

Multiplication and skip counting describe the same thing in two ways. Skip counting describes the process: take equal-sized steps. Multiplication gives the destination a compact label: the 4th stop of 'count by 2s' is labeled 2 × 4. Students who already know skip-counting sequences can immediately make sense of multiplication facts — they're not starting from zero, they're attaching a name to a familiar counting pattern. This is why the 2s, 5s, and 10s come first: they have skip-counting sequences students already know.