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In a farm there are cows and hens. If heads are counted they are 180, if legs are counted they are 420. The number of cows in the farm is
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- 130
- 150
- 50
- 30
Correct Option: D
A cow and a hen each has a head.
If the total number of cows be N, then
Number of hens = 180 – N
A cow has four legs and a hen has two legs.
∴ (180 – N) × 2 + 4N = 420
⇒ 360 – 2N + 4N = 420
⇒ 2N = 420 – 360 = 60
| ⇒ N = | = 30 | |
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