Question: 15.
The diagram below shows rectangular tank A 3/5-filled with water and two empty rectangular tanks B and C. The diameter of the holes on the tanks is 10 cm.
45 cm
17 cm
10 cm
27 cm
22 cm
25 cm
14 cm
12 cm
Tank A
Tank B
Tank C
The stoppers were removed and water flowed from tank A into tank B into tank C.
3 ℓ of water overflowed from tank C in the end.
How much water did tank A contain at first?
Give your answer in litres and millilitres.
1. **State the problem:** We have three rectangular tanks A, B, and C. Tank A is initially filled to 3/5 of its height with water. Water flows from tank A to tank B, then to tank C, and finally 3 liters overflow from tank C. We need to find how much water tank A contained at first in litres and millilitres.
2. **Identify dimensions and volumes:**
- Tank A dimensions: base area unknown, height = 45 cm
- Tank B dimensions: 25 cm × 22 cm × 14 cm
- Tank C dimensions: 22 cm × 15 cm × 12 cm
3. **Calculate volume of water initially in tank A:**
- Height of water in tank A = $\frac{3}{5} \times 45 = 27$ cm
- Base area of tank A is not given explicitly, but we can find it by using the volumes of tanks B and C and the overflow.
4. **Calculate volumes of tanks B and C:**
- Volume of tank B = $25 \times 22 \times 14 = 7700$ cm$^3$
- Volume of tank C = $22 \times 15 \times 12 = 3960$ cm$^3$
5. **Convert overflow volume to cm$^3$:**
- $3$ litres = $3000$ cm$^3$
6. **Total volume of water after flow:**
- Water fills tank B completely (since it was empty), volume = 7700 cm$^3$
- Water fills tank C completely plus 3 litres overflow, so water volume in C before overflow = $3960 + 3000 = 6960$ cm$^3$
7. **Total water volume initially in tank A:**
- Total water = volume in B + volume in C before overflow
- $7700 + 6960 = 14660$ cm$^3$
8. **Calculate base area of tank A:**
- Volume of water in tank A initially = base area $\times$ height of water
- Let base area = $A$ cm$^2$
- $A \times 27 = 14660$
- $A = \frac{14660}{27} \approx 542.96$ cm$^2$
9. **Calculate total volume of tank A:**
- Total volume = base area $\times$ total height = $542.96 \times 45 = 24433.2$ cm$^3$
10. **Convert initial water volume to litres and millilitres:**
- $14660$ cm$^3$ = $14.66$ litres = $14$ litres and $660$ millilitres
**Final answer:** Tank A initially contained **14 litres and 660 millilitres** of water.