Final answer:
To determine the weed's height after 3 weeks, multiply the daily growth rate (0.6 cm/day) by the number of days in 3 weeks (21 days) to find the total growth (12.6 cm), and then add it to the current height of the weed (5.4 cm) for a final height of 18 cm.
Step-by-step explanation:
To calculate how tall the weed will be in 3 weeks, we must first determine the number of days in 3 weeks. Since a week consists of 7 days, 3 weeks would be 3 times 7, which equals to 21 days. The weed is growing at a rate of 0.6 cm per day. To find the total growth over 3 weeks, we multiply the daily growth rate by the number of days:
Total growth = 0.6 cm/day × 21 days
= 12.6 cm
Now, we add the current height of the weed to the total growth to find the height of the weed after 3 weeks:
Final height = current height + total growth = 5.4 cm + 12.6 cm
= 18 cm
Therefore, the weed will be 18 cm tall after 3 weeks.