Operations on Whole Numbers

    $$
    30 \text{ ml/day} \times 15 \text{ days} = \boxed{450 \text{ ml}}
    $$

• b) The distance between Dakshe's house and his school is 7 km.
  • (i) Mathematical expression for total distance traveled in 1 day (to school and back): $$7 \times 2$$
  • (ii) Kilometres traveled in 6 days:

    $$
    14 \text{ km/day} \times 6 \text{ days} = \boxed{84 \text{ km}}
    $$

• c) Mrs. Chamling earns Rs 6,000 in a week. She spends Rs 250 for food and Rs 75 for transportation everyday.
  • (i) Mathematical expression to show her weekly savings: $$6000 - (250 + 75) \times 7$$
  • (ii) Money she saves in a week:

    $$
    6000 \text{ Rs (earnings)} - 2275 \text{ Rs (expenses)} = \boxed{3725 \text{ Rs}}
    $$

• d) Sunayana had 20 marbles. She lost 6 marbles and she divided the rest of them among her 7 friends.
  • (i) Mathematical expression: $$\frac{20 - 6}{7}$$
  • (ii) Marbles each friend would get:

    $$
    \frac{14 \text{ marbles}}{7 \text{ friends}} = \boxed{2 \text{ marbles/friend}}
    $$

• e) Pratik has 300 rupees. He buys 2 boxes at Rs 60 each and 3 pens at Rs 30 each. Write a mathematical expression to show this information. Simplify it and find how much money is left with him?
  • Mathematical expression: $$300 - (2 \times 60 + 3 \times 30)$$
  • Money left with him:

    $$
    300 \text{ Rs} - 210 \text{ Rs} = \boxed{90 \text{ Rs}}
    $$

• f) There are two baskets each of them containing 18 apples. 10 apples are rotten and not fit for eating. You add 4 more apples and then divide among 6 friends. Show this information in a mathematical expression. Simplify it and find how many apples would each friend get?
  • Mathematical expression: $$\frac{((2 \times 18) - 10) + 4}{6}$$
  • Apples each friend would get:

    $$
    \frac{30 \text{ apples}}{6 \text{ friends}} = \boxed{5 \text{ apples/friend}}
    $$

7. It's your time - Project work and Activity Section

• a) Let's make a mathematical expression using the symbols $\div$ and $+$ between the numbers 4, 12 and 8 to get the result 11.

  • Mathematical expression: $$12 \div 4 + 8 = \boxed{11}$$

• b) Let's use the symbol $\div$ and $\times$ between the numbers 5, 20 and 2 at appropriate place to get the result 2. You can use brackets if necessary.

  • Mathematical expression: $$20 \div (5 \times 2) = \boxed{2}$$