Let’s solve each problem step by step.
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Problem 1:
A playschool has 63 boys and 27 girls. What will be the number of boys if there are 9 girls in the school?
We need to keep the
ratio of boys to girls the same.
Original ratio:
Boys : Girls = 63 : 27
Simplify: divide both by 9 → 7 : 3
So for every 3 girls, there are 7 boys.
Now, if there are 9 girls, how many boys?
Since 3 girls → 7 boys,
then 9 girls = 3 × 3 girls → 3 × 7 =
21 boys
✔ Check: 21 : 9 = divide by 3 → 7 : 3 — same as original. ✔️
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Problem 2:
A machine can produce 6 yards of fabric in 2 minutes. How much fabric can the machine produce in 1 hour?
First, find rate per minute:
6 yards in 2 minutes → 6 ÷ 2 =
3 yards per minute
1 hour = 60 minutes
So in 60 minutes: 3 × 60 =
180 yards
✔ Check: 2 min → 6 yd ⇒ 60 min is 30 times longer → 6 × 30 = 180 yd. ✔️
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Problem 3:
12 miles ≈ 19 km. How many km (approx.) are equal to 18 miles?
Set up a proportion:
12 miles → 19 km
18 miles → ? km
Use unit rate:
1 mile ≈ 19 ÷ 12 km = 1.583... km
Then 18 miles ≈ 18 × (19/12) = (18/12) × 19 = (3/2) × 19 = 1.5 × 19 =
28.5 km
Since it says “approx.”, we can round to nearest whole number:
29 km, but 28.5 is exact from the given ratio. Usually in such problems, they expect 28.5 or maybe 29. Let's keep 28.5 unless told to round.
But let’s double-check:
12 mi : 19 km = 18 mi : x km
Cross-multiply: 12x = 18 × 19 = 342
x = 342 ÷ 12 = 28.5 ✔️
So answer:
28.5 km
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Problem 4:
80 boys are attending a picnic. There is a ratio of 3:5 for the number of girls to the number of boys. How many girls are there?
Ratio: girls : boys = 3 : 5
That means for every 5 boys, there are 3 girls.
We have 80 boys. How many groups of 5 boys?
80 ÷ 5 = 16 groups
Each group has 3 girls → 16 × 3 =
48 girls
✔ Check: 48 : 80 = divide by 16 → 3 : 5 ✔️
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Problem 5:
The total weight of 15 boxes is 45 pounds. How much would 40 boxes weigh?
Find weight per box:
45 ÷ 15 =
3 pounds per box
Then 40 boxes: 40 × 3 =
120 pounds
✔ Check: 15 × 3 = 45, so 40 × 3 = 120 ✔️
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Problem 6 (labeled as second 5 — likely a typo, should be #6):
4 spoons cost $12. How much do 16 spoons cost?
Cost per spoon: $12 ÷ 4 = $3 per spoon
16 spoons: 16 × $3 =
$48
✔ Check: 4 spoons = $12 → 16 spoons = 4 × 4 spoons → 4 × $12 = $48 ✔️
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Now compile all final answers in order:
1. 21
2. 180
3. 28.5
4. 48
5. 120
6. 48
Final Answer:
21
180
28.5
48
120
48
Parent Tip: Review the logic above to help your child master the concept of 7th grade math ratios and proportions worksheet.