Step by step
The question
Question: A bird is at 6 m.
It dives 9 m.
Where is it now?
1 Write it as a sum
We start at 6.
Dives means down: take away 9.
6 − 9
Sea level is 0.
Below it is negative.
6 m above sea level
dives 9 → − 9
2 Work it out
Start at 6.
Go down 9.
We pass 0.
Careful!
We start at 6, not at 6.
Keep the minus sign.
Careful: not 6 − 9 = -3 ✗
We land on −3 m.
= −3 m
So the answer is −3 m: 3 meters below sea level.
3 Check
Let's check: go back.
−3 plus 9 is 6, where we started.
So the answer is right!
−3 + 9 = 6
Let's look back.
First: write it as a sum.
Then: work it out.
Last: check.
Answer
= −3 m