A tractor can plough the same area of a field 4 times faster than a pair of oxen. A farmer wants to plough Class 8
easyA tractor can plough the same area of a field 4 times faster than a pair of oxen. A farmer wants to plough Class 8
Question 1.
A tractor can plough the same area of a field 4 times faster than a pair of oxen. A farmer wants to plough his 20- acre field. A pair of oxen takes 6 hours to plough an acre of land. How much time would it take if the farmer used a pair of oxen to plough the field? How much time would it take him if he decides to use a tractor instead? Class 8
Solution:
Time taken by a pair of oxen to plough 20 acres of land
= 20 × 6 hours
= 120 hours
Time taken by a tractor to plough the same 20 acres of land
= [latex]\frac{120}{4}[/latex] = 30 hours, because tractor is 4 4
times faster than a pair of oxen.
Question 2.
The ₹ 10 coin is an alloy of copper and nickel called ‘cupro-nickel’. Copper and nickel are mixed in a 3 : 1 ratio to get this alloy. The mass of the coin is 7.74 grams. If the cost of copper is ₹ 906 per kg and the cost of nickel is ₹ 1,341 per kg, what is the cost of these metals in a ₹ 10 coin? Class 8
Solution:
Mass of copper in 7.74 grams of a ₹ 10 coins
= [latex]\frac{7.74}{(3+1)}[/latex] × 3 gram
= [latex]\frac{7.74 \times 3}{4}[/latex]gram = [latex]\frac{774 \times 3}{400}[/latex]gram
= [latex]\frac{387 \times 3}{200}[/latex]gram
So, cost of copper in this coin
= ₹ 5.25933 = ₹ 5.26 (approx.)
Mass of nickel in 7.74 gram of ₹ 10 coin
= [latex]\frac{7.74}{(3+1)}[/latex] × 1 gram = [latex]\frac{774}{400}[/latex] gram
= [latex]\frac{387}{200}[/latex] gram
So, cost of nickel in the coin
= ₹ [latex]\frac{1341}{1000} \times \frac{387}{200}[/latex]
= ₹ 2.59483 = ₹ 2.60 (approx.)