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A person’s heart beats approximately $10^5$ times each day - Edexcel - GCSE Maths - Question 11 - 2020 - Paper 3

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A person’s heart beats approximately $10^5$ times each day. A person lives for approximately 81 years. (a) Work out an estimate for the number of times a person’s h... show full transcript

Worked Solution & Example Answer:A person’s heart beats approximately $10^5$ times each day - Edexcel - GCSE Maths - Question 11 - 2020 - Paper 3

Step 1

Work out an estimate for the number of times a person’s heart beats in their lifetime.

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Answer

To estimate the number of heartbeats in a lifetime:

  1. Determine the number of heartbeats per year:

    105 beats/day×365 days/year=3.65×107 beats/year10^5 \text{ beats/day} \times 365 \text{ days/year} = 3.65 \times 10^7 \text{ beats/year}

  2. Calculate the total number of heartbeats over 81 years:

    3.65×107 beats/year×81 years≈2.95×109 beats3.65 \times 10^7 \text{ beats/year} \times 81 \text{ years} \approx 2.95 \times 10^9 \text{ beats}

  3. Rounding to two significant figures gives:

    3.0×109 beats3.0 \times 10^9 \text{ beats}

Step 2

Work out the average mass of 1 red blood cell.

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Answer

Given that 2 x 101210^{12} red blood cells have a total mass of 90 grams:

  1. Calculate the mass of one red blood cell:

    Average mass=90 grams2×1012=45×10−12 grams\text{Average mass} = \frac{90 \text{ grams}}{2 \times 10^{12}} = 45 \times 10^{-12} \text{ grams}

  2. Convert to standard form:

    4.5×10−11 grams4.5 \times 10^{-11} \text{ grams}

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