Mixed Problems
1. **Calculate the length of the rod**
The rod forms a right triangle with the wall and the ground.
Given:
- Distance from foot of rod to wall (base) = 3.6 m
- Height of rod above ground = 4.8 m
Use Pythagoras theorem:
$$\text{Length} = \sqrt{(3.6)^2 + (4.8)^2}$$
$$= \sqrt{12.96 + 23.04} = \sqrt{36} = 6 \text{ m}$$
2. **Calculate the density of the rod**
Given:
- Volume = 600 cm³
- Mass = 2.4 kg
Density formula:
$$\text{Density} = \frac{\text{Mass}}{\text{Volume}} = \frac{2.4}{600} = 0.004 \text{ kg/cm}^3$$
3. **Determine the local time at town P**
Given:
- Town Q longitude = 40°E
- Town P longitude = 50°W
- Local time at Q = 4:00 p.m.
Total longitude difference:
$$40 + 50 = 90^\circ$$
Each 15° corresponds to 1 hour time difference:
$$\frac{90}{15} = 6 \text{ hours}$$
Town P is west of Q, so local time at P is:
$$4:00 \text{ p.m.} - 6 \text{ hours} = 10:00 \text{ a.m.}$$
4. **Calculate import duty, excise duty, and VAT**
Customs value = 1,200,000
(a) Import duty at 20%:
$$1,200,000 \times 0.20 = 240,000$$
(b) Excise duty at 18%:
$$1,200,000 \times 0.18 = 216,000$$
(c) VAT at 16%:
VAT is charged on customs value + import duty + excise duty:
$$\text{VAT base} = 1,200,000 + 240,000 + 216,000 = 1,656,000$$
$$\text{VAT} = 1,656,000 \times 0.16 = 264,960$$
5. **Thanksgiving ceremony attendance**
Ratio men:women:children = 5:7:3
Children = 60
Find the multiplier:
$$\frac{60}{3} = 20$$
(a) Number of men:
$$5 \times 20 = 100$$
(b) Number of women:
$$7 \times 20 = 140$$
Difference women - men:
$$140 - 100 = 40$$
6. **Packing flour problem**
5 men work 6 hours/day for 12 days:
Total man-hours:
$$5 \times 6 \times 12 = 360$$
3 men work 8 hours/day, let days = $d$:
$$3 \times 8 \times d = 360$$
$$24d = 360 \Rightarrow d = \frac{360}{24} = 15$$
More days taken:
$$15 - 12 = 3 \text{ days}$$
7. **Express decimal 0.17 as fraction**
$$0.17 = \frac{17}{100}$$
8. **Name of quadrilateral with given properties**
- Opposite sides equal
- Diagonals bisect at 90°
- Opposite angles equal
This describes a rhombus.
9. **Length of wall on drawing**
Scale 1:100, actual length = 3 m = 300 cm
Drawing length:
$$\frac{300}{100} = 3 \text{ cm}$$
10. **Gradient of line L₂ perpendicular to L₁**
Given L₁: $2y = x + 3 \Rightarrow y = \frac{1}{2}x + \frac{3}{2}$
Gradient of L₁ = $\frac{1}{2}$
Gradient of L₂ (perpendicular) = negative reciprocal:
$$-2$$
11. **New length of photograph**
Original length = 16 cm
Enlarged to twice size:
$$16 \times 2 = 32 \text{ cm}$$