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A took 15 sec. to cross a rectangular field diagonally walking at the rate of 52 m/min. and B took the same time to cross the same field along its sides walking at the rate of 68 m/ min. The area of the field is :
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- 30 m²
- 40 m²
- 50 m²
- 60 m²
- 30 m²
Correct Option: D
Using Rule 9, 
BD = length of diagonal = speed × time
| = | × 15 = 13 metre | |
| 60 |
BD = √l² + b&up2;
⇒ l² + b² = 169 ...(i)
Again,
| (l + b) = | × 15 = 17........(ii) | |
| 60 |
∴ (l + b)² = l² + b² + 2lb
⇒ 172 = 169 + 2 lb
⇒ 2 lb = 289 – 169 = 120
| ⇒ lb = | 60m² | |
| 2 |
