Question

about 10 cm about 10 cm about 20 cm about 30 cm about 40 cm

Explanation:

Step1: Observe the length comparison

The purple - bar is about 10 cm and the wrench is approximately twice as long as the purple - bar.

Step2: Calculate the length of the wrench

Since the wrench is about twice 10 cm, we have $2\times10 = 20$ cm.

Answer:

About 20 cm