Estimation (Intro) — Answer Key
Part A: Multiple Choice
Circle the best answer for each question.
1. Sam has $18 and buys a $7 book. About how much is left?
A) About $10
B) About $20
C) About $5
D) About $25
$20 - $10 = $10, and the exact $11 is very close, so 'about $10' is the best estimate.
2. Mia has $32. She buys a $19 toy. Estimate how much she has left.
A) About $10
B) About $20
C) About $15
D) About $5
$30 - $20 = $10, which is close to the exact $13 left, so 'about $10' fits best.
3. Jon buys snacks for $14 and $27. About how much did he spend total?
A) About $40
B) About $50
C) About $30
D) About $20
$10 + $30 = $40, which is very close to the exact $41, so 'about $40' is best.
4. Kim has $48. She says she can spend $52 today. Is that reasonable?
A) No, $52 is more than $48
B) Yes, $52 is close to $48
C) Yes, $52 is less than $48
D) No, $48 is more than $52
You cannot spend more than you have; $52 is greater than $48, so the plan is not reasonable.
Part B: Fill in the Blank
Write the correct answer on each line.
1. Sam: $18 - $7 rounds to $20 - $10 = $10.
$20 - $10 = $10, close to the exact $11, showing how estimation previews the real change.
2. Mia: $32 - $19 rounds to $30 - $20 = $10.
$30 - $20 = $10, near the exact $13, giving a quick idea of remaining money.
3. Jon: $14 + $27 rounds to $10 + $30 = $40.
$10 + $30 = $40 is nearly equal to the exact $41 total spent.
4. An estimate in money helps decide if you have enough cash.
A quick estimate tells you if your money covers the cost before you do the exact math.
5. If estimate says $10 left but exact is $11, the exact is reasonable.
$11 and $10 differ by only $1, so the exact answer is reasonable and close to the estimate.