Question

Length of the stem at time 0 is 20 cm. The arithmetic growth rate is 30 cm per day. What is the length of the stem at the end of the 7th day?

• A. 460 cm
• B. 50 cm
• C. 170 cm
• D. 230 cm

Hint:

Arithmetic growth means constant increase per unit time. Always use formula \(L_t=L_0+rt\) where growth rate remains fixed.

Answer 1

The Correct Option is D

Step 1: Recall arithmetic growth.
In arithmetic growth the length increases by a fixed amount each day, so we use $L_t = L_0 + rt$.
Step 2: Note the initial length.
Here $L_0 = 20$ cm at time zero.
Step 3: Note the growth rate.
The rate is $r = 30$ cm per day.
Step 4: Note the time.
The time is $t = 7$ days.
Step 5: Substitute and compute.
$L_t = 20 + (30 \times 7) = 20 + 210 = 230$ cm.
Step 6: Conclude.
So after 7 days the stem is 230 cm long, which is option 4.
\[ \boxed{230\ \text{cm}} \]