1. **State the problem:** The population of a town is 39505406. We need to write it in words. 2. **Write the number in words:** 39505406 is read as Thirty-nine million five hundred five thousand four hundred six. 1. **State the problem:** Round off the population 39505406 to the nearest million. 2. **Recall rounding rule:** To round to the nearest million, look at the hundred-thousands digit (the digit right after the millions place). 3. **Apply rounding:** The millions digit is 9 (in 39 million), the hundred-thousands digit is 5. 4. Since the hundred-thousands digit is 5 or more, we round up the millions digit. 5. So, 39 million rounds up to 40 million. 1. **State the problem:** A cube has side length 2.4 m. Find its volume. 2. **Formula:** Volume of cube $V = s^3$ where $s$ is the side length. 3. Calculate: $$V = (2.4)^3 = 2.4 \times 2.4 \times 2.4$$ 4. Calculate stepwise: $2.4 \times 2.4 = 5.76$ 5. Then $5.76 \times 2.4 = 13.824$ 6. So, volume $V = 13.824$ cubic meters. 1. **State the problem:** Smaller cubes of side 40 cm are packed into the larger cube of side 2.4 m. Find how many smaller cubes fit. 2. **Convert units:** 2.4 m = 240 cm. 3. **Find volume of smaller cube:** $0.4$ m or 40 cm side, volume $= 0.4^3 = 0.064$ m³ or $40^3 = 64000$ cm³. 4. **Find volume of larger cube:** $2.4^3 = 13.824$ m³ or $240^3 = 13824000$ cm³. 5. **Number of smaller cubes:** $$\frac{\text{Volume of large cube}}{\text{Volume of small cube}} = \frac{13.824}{0.064}$$ 6. Simplify: $$\frac{13.824}{0.064} = \frac{\cancel{13.824}}{\cancel{0.064}} = 216$$ 1. **State the problem:** A cyclist covers 5000 m in 30 minutes. Find speed in km/h. 2. **Convert distance to km:** $5000$ m = $5$ km. 3. **Convert time to hours:** $30$ minutes = $0.5$ hours. 4. **Speed formula:** $\text{speed} = \frac{\text{distance}}{\text{time}}$ 5. Calculate speed: $$\frac{5}{0.5} = 10$$ km/h. 1. **State the problem:** Convert speed 10 km/h to m/s. 2. **Conversion factor:** $1$ km/h = $\frac{1000}{3600} = \frac{5}{18}$ m/s. 3. Calculate: $$10 \times \frac{5}{18} = \frac{50}{18} = \frac{25}{9} \approx 2.78$$ m/s. 1. **State the problem:** Temperature changes from 26°C to 10°C. Find change in Kelvin. 2. **Recall:** Change in temperature in Celsius equals change in Kelvin. 3. Calculate change: $$26 - 10 = 16$$ K. 1. **State the problem:** Form algebraic expression for sum of two consecutive numbers where the greater number doubled plus smaller number equals $r$. 2. Let smaller number be $x$, then greater number is $x+1$. 3. Given: $2(x+1) + x = r$ 4. Simplify: $$2x + 2 + x = r$$ 5. Combine like terms: $$3x + 2 = r$$ 6. Sum of two numbers: $$x + (x+1) = 2x + 1$$ **Final answers:** 21a) Thirty-nine million five hundred five thousand four hundred six. 21b) 40 million. 22a) Volume = 13.824 m³. 22b) Number of smaller cubes = 216. 23a) Speed = 10 km/h. 23b) Speed = 2.78 m/s. 24) Change in temperature = 16 K. 25) Sum of two consecutive numbers = $2x + 1$ where $3x + 2 = r$.