# Double Promotional Examination Primary 4 Mathematics

**Worked Out Solution **

**DOUBLE PROMOTIONAL EXAMINATION 2024**

**SUBJECT: MATHEMATICS**

**NAME:**

**1. Mr. Benson wants to sort out his computer files into folders that hold 30 files each. He has 960 files. About how many folders will Mr. Benson need to hold all the files?**

**Workings:** 960 files ÷ 30 files per folder = 32 folders

**Answer:** 32 folders

**2. Find the length of the longest side of a right-angled triangle if the other sides are 8 cm and 6 cm**

**Workings:** Using Pythagoras’ theorem: Hypotenuse = √(8² + 6²) = √(64 + 36) = √100 = 10 cm

**Answer:** 10 cm

**3. If 15 men can construct a bridge over a river in 120 days, how many men can construct the bridge in 45 days working at the same rate?**

**Workings:** Number of men = (15 men × 120 days) ÷ 45 days = 1800 ÷ 45 = 40 men

**Answer:** 40 men

**4. A man spent 5/8 of his salary on food and 2/5 of the remainder on clothes. What fraction of his salary is left?**

**Workings:** Remainder after food: 1 – 5/8 = 3/8 Spent on clothes: 2/5 × 3/8 = 6/40 = 3/20 Fraction left: 3/8 – 3/20 = 15/40 – 6/40 = 9/40

**Answer:** 9/40

**5. Two of the angles in a triangle are 40° and 100°. This triangle is a/an ________ triangle.**

**Explanation:** Since one angle is greater than 90°, it is an obtuse-angled triangle.

**Answer:** Obtuse-angled

**6. Divide 10 by half. Add 10 and divide again by half. The result is**

**Workings:** 10 ÷ 0.5 = 20 20 + 10 = 30 30 ÷ 0.5 = 60

**Answer:** 60

**7. How many minutes are there from 11:37 am to 1:15 pm?**

**Workings:** 1:15 pm – 11:37 am = 1 hour 38 minutes 1 hour 38 minutes = 60 + 38 = 98 minutes

**Answer:** 98 minutes

**8. Subtracting the largest two-digit number from the largest three-digit number and dividing the result by the smallest three-digit number, we get**

**Workings:** (999 – 99) ÷ 100 = 900 ÷ 100 = 9

**Answer:** 9

**9. Calculate to the nearest whole number, the volume of a cylinder with diameter 26 cm and height 7.5 cm (π = 3.14)**

**Workings:** Radius = 13 cm (since diameter = 26 cm) Volume = π × r² × h = 3.14 × 13² × 7.5 ≈ 3980 cm³

**Answer:** 3980 cm³

**10. Change 4 hrs. 15 mins 18 secs to seconds**

**Workings:** 4 hours = 4 × 3600 = 14400 seconds 15 minutes = 15 × 60 = 900 seconds 18 seconds Total = 14400 + 900 + 18 = 15318 seconds

**Answer:** 15318 seconds

**11. Write in numerals One billion, fifty-seven thousand, three hundred and eight**

**Answer:** 1,000,057,308

**12. Round off 2.0052 to 3 significant figures**

**Answer:** 2.01

**13. What is 10% of 10% of 1000?**

**Workings:** 10% of 1000 = 100 10% of 100 = 10

**Answer:** 10

**14. If the cost of 5 mangoes is 40 kobo and that of 4 oranges is 24 kobo, find the cost of 3 mangoes and 5 oranges**

**Workings:** Cost of 1 mango = 40 kobo ÷ 5 = 8 kobo Cost of 1 orange = 24 kobo ÷ 4 = 6 kobo Cost of 3 mangoes and 5 oranges = (3 × 8 kobo) + (5 × 6 kobo) = 24 kobo + 30 kobo = 54 kobo

**Answer:** 54 kobo

**15. What percentage of 200 is 250?**

**Workings:** (250 ÷ 200) × 100 = 125%

**Answer:** 125%

**16. A group of men and dogs are in a park. In all, there are 22 heads and 72 feet. How many dogs are in the park?**

**Workings:** Let x be the number of men and y be the number of dogs. x + y = 22 2x + 4y = 72 Solving these equations: x + 2y = 36 Subtracting the first equation from this: (x + 2y) – (x + y) = 36 – 22 y = 14

**Answer:** 14 dogs

**17. Express the percentage 43% as a decimal**

**Answer:** 0.43

**18. A farmer is four times as old as his daughter. If the daughter is q years old, how old is he?**

**Answer:** 4q years

## SECTION B: THEORY

**When I multiply the number 49 and m together, my result is 2401. What is the value of m?**Solution: 49 multiplied by m equals 2401. Therefore, m = 2401 ÷ 49, which equals 49.Therefore, m = 49.

**Add up MML and MXCII, giving your answer in Arabic numerals.**Solution: MML equals 1050, and MXCII equals 1092. Adding these together, 1050 + 1092 equals 2142.Therefore, the answer is 2142.

**Tom is the 20th best and 20th worst athlete on his team. How many athletes are on the team?**Solution: If Tom is both the 20th best and the 20th worst, there are 19 athletes better than him and 19 worse than him. Therefore, the total number of athletes is 19 + 1 (Tom) + 19, which equals 39.Therefore, there are 39 athletes on the team.

**The cells of some kind of bacteria divide into two every 30 minutes. If you begin with a single cell, how many cells will be there after three hours?**Solution: Three hours is 180 minutes. The number of divisions in 180 minutes is 180 ÷ 30, which equals 6. Therefore, the number of cells is 2^6, which equals 64.Therefore, there will be 64 cells after three hours.

**An express train leaves Lagos at 4:00pm on Monday. It arrives in Maiduguri at 11:00am on Wednesday. How long does the journey take?**Solution: From 4:00pm Monday to 4:00pm Tuesday is 24 hours. From 4:00pm Tuesday to 11:00am Wednesday is 19 hours. Adding these together, 24 + 19 equals 43 hours.Therefore, the journey takes 43 hours.

**Express 3 meters in millimeters.**Solution: 1 meter equals 1000 millimeters. Therefore, 3 meters equals 3 x 1000, which equals 3000 millimeters.Therefore, 3 meters is equal to 3000 millimeters.

**The mean of three numbers is 3. The mode is 4. What is the lowest number?**Solution: Let the three numbers be a, b, and c. The mean is (a + b + c) ÷ 3 = 3, so a + b + c = 9. The mode is 4, meaning 4 appears most frequently. Therefore, two of the numbers are 4. So, 4 + 4 + c = 9, which means c = 1.Therefore, the lowest number is 1.

**I think of a number, I add 2 and then subtract 21. The result is 22. What was the number I thought of?**Solution: Let the number be x. x + 2 – 21 = 22, so x – 19 = 22, which means x = 41.Therefore, the number is 41.

**Find the total weight of 5 tins when each tin weighs 470 grams.**Solution: The total weight is 5 x 470, which equals 2350 grams.Therefore, the total weight is 2350 grams.

**How many 300 grams of flour can be filled from a sack containing 84kg?**

Solution: 84kg equals 84000 grams. The number of 300 grams portions is 84000 ÷ 300, which equals 280.

Therefore, 280 portions of 300 grams each can be filled.