Operations on Whole Numbers

Here are the solutions to the problems: 6. Operations on Whole Numbers a) A sick person takes 10 ml of medicine three times a day. (i) Mathematical expression: 10 × 3 (ii) Medicine taken in 15 days: Step 1: Calculate medicine per day. 10 ml/dose × 3 doses/day = 30 ml/day Step 2: Calculate medicine in 15 days. 30 ml/day × 15 days = 450 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 × 2 (ii) Kilometres traveled in 6 days: Step 1: Calculate distance traveled in 1 day. 7 km/way × 2 ways/day = 14 km/day Step 2: Calculate distance traveled in 6 days. 14 km/day × 6 days = 84 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) × 7 (ii) Money she saves in a week: Step 1: Calculate daily expenses. 250 Rs (food) + 75 Rs (transport) = 325 Rs/day Step 2: Calculate weekly expenses. 325 Rs/day × 7 days/week = 2275 Rs/week Step 3: Calculate weekly savings. 6000 Rs (earnings) - 2275 Rs (expenses) = 3725 Rs d) Sunayana had 20 marbles. She lost 6 marbles and she divided the rest of them among her 7 friends. (i) Mathematical expression: (20 - 6)/(7) (ii) Marbles each friend would get: Step 1: Calculate remaining marbles. 20 marbles - 6 marbles lost = 14 marbles Step 2: Divide remaining marbles among 7 friends. 14 marbles7 friends = 2 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 × 60 + 3 × 30) Money left with him: Step 1: Calculate cost of boxes. 2 × 60 Rs = 120 Rs Step 2: Calculate cost of pens. 3 × 30 Rs = 90 Rs Step 3: Calculate total money spent. 120 Rs + 90 Rs = 210 Rs Step 4: Calculate money left. 300 Rs - 210 Rs = 90 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: (((2 × 18) - 10) + 4)/(6) Apples each friend would get: Step 1: Calculate initial total apples. 2 baskets × 18 apples/basket = 36 apples Step 2: Subtract rotten apples. 36 apples - 10 rotten apples = 26 apples Step 3: Add new apples. 26 apples + 4 new apples = 30 apples Step 4: Divide among friends. 30 apples6 friends = 5 apples/friend 7. It's your time - Project work and Activity Section a) Let's make a mathematical expression using the symbols ÷ and + between the numbers 4, 12 and 8 to get the result 11. Mathematical expression: 12 ÷ 4 + 8 = 11 b) Let's use the symbol ÷ and × between the numbers 5, 20 and 2 at appropriate place to get the result 2. You can use brackets if necessary. Mathematical expression: 20 ÷ (5 × 2) = 2 Last free one today — make it count tomorrow, or type /upgrade for unlimited.