A newborn baby has an approximate mass of 3.5 kilograms - OCR - GCSE Maths - Question 22 - 2018 - Paper 1

To find the number of human cells in a newborn baby, we can use the formula:

$$ext{Number of Cells} = \frac{ ext{Mass of Baby}}{ ext{Mass of One Cell}}$$

1. Convert the mass of the baby from kilograms to grams:

   • The mass of the baby is approximately 3.5 kg, which is equal to:
   $$3.5 ext{ kg} = 3.5 \times 10^3 ext{ grams}$$

2. Use the mass of one human cell, which is approximately 2.7 × 10⁻¹¹ grams.

3. Now, substitute these values into the formula:

   $$ext{Number of Cells} = \frac{3.5 \times 10^3}{2.7 \times 10^{-11}}$$

4. To perform the division, first simplify:

   • Calculate the coefficients:
   $$\frac{3.5}{2.7} \approx 1.296$$
   • Calculate the powers of ten:
   $$10^3 \div 10^{-11} = 10^{3 - (-11)} = 10^{3 + 11} = 10^{14}$$

5. Put it all together:

   • The number of cells becomes:
   $$ext{Number of Cells} \approx 1.296 \times 10^{14}$$

6. Round this to 2 significant figures:

   • The final answer is:
   $$1.3 \times 10^{14}$$