Lesson 8 of 11
A question, start to finish
Show on a big screenA long question is easier in steps. Solve it one step at a time.
Step 1 of 7
- Read the question first — what job, what units.
- Split the object into its two solids.
- Find what the question never gave you.
- Pick only the faces that job buys.
- Compute the answer once, from the picked faces.
- Answer with the units the question asked for.
- A wrong shortcut: using the height as the slant.
The steps
"A toy is a cone on a hemisphere of radius 21. It is 49 tall. Paint costs 50 paise per square unit. Find the cost in rupees."
100 paise make ₹1. So 50 paise is ₹0.50.
- Read. Painting covers the outside. We need an area first.
- Split. A cone sits on a hemisphere. Both have radius 21.
- Missing. The cone is 49 − 21 = 28 tall. Then l² = 21² + 28² = 1225, so l = 35.
- Pick. Count the cone skin and the dome skin. Cone skin = 22/7 × 21 × 35 = 2310. Dome skin = 2 × 22/7 × 21 × 21 = 2772.
- Compute. 2310 + 2772 = 5082. Then 5082 × 0.50 = 2541.
- Answer. The cost is ₹2541.
Read the job. Split the object into solids. Find the missing length. Pick the faces the job counts. Compute once, then answer in the asked unit.
Tap Next step to solve it.
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