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4 questions · self-marked practice — reveal the answer and mark yourself.

Question 14 Marks
Calculate and write the answer in scientific notation :
(i) If each person in the world had 30 pieces of clothing, find the total number of pieces of clothing.
(ii) There are about 100 million bee colonies in the world. Find the number of honeybees if each colony has about 50,000 bees.
(iii) The human body has about 38 trillion bacterial cells. Find the bacterial population residing in all humans in the world.
(iv) Total time spent eating in a lifetime in seconds.
Answer
(i) Estimated world population: $\approx 8$ billion $=8 \times 10^9$
Number of pieces of clothing each person had $=30$ pieces
Total number of pieces of clothing $=8 \times 10^9 \times 30=2.4 \times 10^{11}$
(ii) Number of bee colonies in the world $=100$ million $=1 \times 10^8$
Number of bees in each colony $=50,000=5 \times 10^4$
Total number of honeybees $=1 \times 10^8 \times 5 \times 10^4=5 \times 10^{12}$
(iii) World population $\approx 8 \times 10^9$
Number of bacterial cells in human body $=38$ trillion $=3.8 \times 10^{13}$
Total bacterial population residing in all humans in the world $=\left(3.8 \times 10^{13}\right) \times\left(8 \times 10^9\right)=30.4 \times 10^{22}=3.04 \times 10^{23}$
(iv) Average person's lifespan $=80$ years
Time spent eating daily $=1.5$ hours
Total eating time per day in seconds $=1.5 \times 3600=5400$ seconds
Number of days in 80 years $=80 \times 365=29,200$
Total seconds spent eating in a lifetime in seconds $=5400 \times 29,200=1.5768 \times 10^8$
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Question 24 Marks
A dairy plans to produce 8.5 billion packets of milk in a year. They want a unique ID (identifier) code for each packet. If they choose to use the digits 0–9, how many digits should the code consist of?
Answer
8.5 billion = 8,500,000,000
Number of DigitsMax Unique Numbers
110 (0 to 9)
210 x 10 = 100
310 x 10 x 10 = 1,000
410,000
5100,000
61,000,000
710,000,000
8100,000,000
91,000,000,000
1010,000,000,000

Therefore, the code should contain at least 10 digits to get a unique ID for each packet.
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Question 34 Marks
If $12^2=144$ what is
(i) $(1.2)^2$
(ii) $(0.12)^2$
(iii) $(0.012)^2$
(iv) $120^2$
Answer
(i) $(1.2)^2=\left(\frac{12}{10}\right)^2=\frac{12^2}{10^2}=\frac{144}{100}=1.44$
(ii) $(0.12)^2=\left(\frac{12}{100}\right)^2=\frac{12^2}{100^2}=\frac{144}{10000}=0.0144$
(iii) $(0.012)^2=\left(\frac{12}{1000}\right)^2=\frac{12^2}{1000^2}=\frac{144}{1000000}=0.000144$
(iv) $120^2=120 \times 120=14,400$
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Question 44 Marks
Express the following numbers in standard form.
(i) 59,853
(ii) 65,950
(iii) 34,30,000
(iv) 70,04,00,00,000
Answer
self
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