Idea 11of 23Builds onExpression or equation?
Equals means the same value
What does the equals sign really mean?
Today you'll discover
- why 9 = 5 + 4 is true
- what a tipped balance means
- how both sides can be sums
Think first9 on one pan; 5 and 4 on the other
Is 9 = 5 + 4 true?
Decide first, then press Next. Ask: do both sides have the same value?
A pan balance held level: a 9 block on the left pan, 5 and 4 blocks on the right. Let go, it stays level, with 9 under each pan. Then 5 and 4 against 9 and 1: it tips toward the 10. Then 6 and 4 against 7 and 3: level. The last step shows 8 and 7 on the left, a box marked x and a 5 block on the right.
See the whole ideathe big idea and the key word, in one place
The big idea
The equals sign means both sides have the same value, like a level balance.
Compare themTrue: 9 = 5 + 4 and 6 + 4 = 7 + 3. Not true: 5 + 4 = 9 + 1, because 9 and 10 are different.
Easy to get wrongThe number after = is not always the answer. In 8 + 7 = x + 5, x is 10, not 15.
Key word
- equals sign
- the sign =, which says both sides have the same value
Ready to use it?
- Decide whether an equation is true.
- Find a missing number that keeps both sides equal.