Question

A plant was 90 cm tall when it was planted. it grows by equal no. of cms each year . At the end of 7th year it was 1/9th taller than at the end of sixth year. how tall was the plant at the end of 12th year?

Answer 1

Let the cms tree grows each year be x
height of tree after 7 years = 7x+90
height of tree after 6 years = 6x+90
therefore 7x+90 = 9(6x+90)
i.e. 7x+90 = 54x+810
i.e. 54x-7x = 810-90
i.e. 47x = 720
i.e. x = 15.3
at the end of 12 years height = 90+12*15.3 = 273.6

Answer 2

The plant at the end of 12th year is, 273.6cm.

What does plant height mean?

• Theoretically, plant height is defined as the shortest distance between the upper boundary (the highest point) of the main photosynthetic tissues (excluding inflorescences) and the ground level.

How do you calculate plant growth?

• To measure a plant's growth rate, use a ruler or measuring tape to measure from the base of the plant to its highest point.
• If your plant is in a pot, start your measurement at the base of the pot.
• Write the measurement down, then repeat 2-3 days later.

According to the question:

Let the cms tree grows each year be x.

Height of tree after 7 years = 7x+90.

Height of tree after 6 years = 6x+90.

Therefore, 7x+90 = 9(6x+90).

i.e. 7x+90 = 54x+810.

i.e. 54x-7x = 810-90.

i.e. 47x = 720.

i.e. x = 15.3.

At the end of 12 years height = 90+12*15.3 = 273.6.

Hence, at the end of 12 years height are 273.6.

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