Tape Measure Errors
1. **Problem:** Given that the measured distance AB is 165.20 m using a 50 m tape that is 0.01 m too short, we want to find the correct distance AB.
2. **Step 1: Understand the meaning of tape length error**
The tape is shorter than the standard by 0.01 m per 50 m, so every measurement on the tape underestimates the actual length.
3. **Step 2: Calculate the correction factor**
The actual tape length is $50 + 0.01 = 50.01$ m but the tape reads 50 m.
Correction factor $= \frac{50.01}{50} = 1.0002$
4. **Step 3: Calculate the correct distance**
Correct distance $= 165.20 \times 1.0002 = 165.23304$ m (approximately).
---
5. **Problem:** A rectangular lot has a correct area of 2 hectares (20000 m²), length is twice the width. The sides were measured with a 50 m tape that is 0.02 m too long. Find error in area in sq. meters.
6. **Step 1: Define variables**
Let width $= w$, length $= 2w$.
Area $= l \times w = 2w \times w = 2w^2 = 20000$ m²
Solve for $w$:
$$2w^2=20000 \Rightarrow w^2=10000 \Rightarrow w=100 \text{ m}$$
Length $l=200$ m.
7. **Step 2: Effect of tape being too long**
The tape length is nominally 50 m but actually $50.02$ m.
Correction factor for measured distances:
$$\text{Correction factor} = \frac{50}{50.02} = 0.9996$$
Because when using the tape, measured lengths are longer than actual, so the actual measured side lengths are shorter.
8. **Step 3: Calculate the measured sides**
Measured width = $w_{meas} = w / 0.9996 = 100.04$ m
Measured length = $l_{meas} = 200 / 0.9996 = 200.08$ m
9. **Step 4: Calculate the measured area using the incorrect tape length**
$$A_{meas} = l_{meas} \times w_{meas} = 200.08 \times 100.04 = 20016.004 \text{ m}^2$$
10. **Step 5: Calculate the error in area**
$$\text{Error} = A_{meas} - A_{correct} = 20016.004 - 20000 = 16.004 \text{ m}^2$$
---
11. **Problem:** Distance BC measured at 146.5 m using a 100 m tape which is 0.015 m too short. Find the correct distance.
12. **Step 1: Correction factor**
Actual tape length = $100 + 0.015 = 100.015$ m
Correction factor = $\frac{100.015}{100} = 1.00015$
13. **Step 2: Calculate correct distance**
$$\text{Correct distance} = 146.5 \times 1.00015 = 146.521975 \text{ m}$$
---
14. **Problem:** The correct distance AB is 213.50 m. Tape length 100 m is 0.025 m too long. Find the measured distance.
15. **Step 1: Calculate tape correction factor**
Actual tape length = $100 - 0.025 = 99.975$ m (because tape is too long, each measurement is shorter)
Correction factor = $\frac{99.975}{100} = 0.99975$
16. **Step 2: Calculate measured distance**
$$\text{Measured distance} = 213.50 \times 0.99975 = 213.446625 \text{ m}$$
---
17. **Problem:** Correct distance CD is 195 m. Tape 50 m is 0.015 m too short. Find measured distance.
18. **Step 1: Correction factor**
Actual tape length = $50 + 0.015 = 50.015$ m
Correction factor = $\frac{50.015}{50} = 1.0003$
19. **Step 2: Calculate measured distance**
$$\text{Measured distance} = 195 \times \frac{50}{50.015} = 195 \times 0.9997 = 194.94 \text{ m}$$
**Final concise answers:**
2. Correct distance AB $\approx 165.23$ m
3. Error in area $\approx 16$ m²
4. Correct distance BC $\approx 146.52$ m
5. Measured distance AB $\approx 213.45$ m
6. Measured distance CD $\approx 194.94$ m