Question

John records the growth of a plant as a bar graph. If he were to calculate the height of the plant in the 5th week by finding the average growth rate, how tall would the plant be?

Week

• A. 100 cm
• B. 71.67 cm
• C. 135 cm
• D. 68.75 cm

Answer 1

The correct option is B 71.67 cm

To find the average growth rate, we calculate the height the plant has grown in consecutive weeks.

$Growthfromweek1toweek2$

$=\text{Height in week 2}–\text{Height in week 1}$
$=35cm–25cm$
$=10cm$

$Growthfromweek2toweek3$

$=\text{Height in week 3}–\text{Height in week 2}$
$=40cm–35cm$
$=5cm$

$Growthfromweek3toweek4$

$=\text{Height in week 4}–\text{Height in week 3}$
$=60cm–40cm$
$=20cm$

$Averagegrowthrate=\frac{10+5+20}{3}\approx 11.67cm$

$HeightinWeek5$

$=\text{Height in week 4}+\text{Average growth rate}$
$=60cm+11.67cm$
$=71.67cm$