Answer: 3.9 gigawatts
Step-by-step explanation:
Using the idea of proportion;
If 7 giants = 1.3 gigawatts
21 giants = x gigawatts
We cross multiply
7 × X = 21 × 1.3
7X = 27.3
We divide bothside by 7 to get the value of x
7X/7 = 27.3/7
x = 3.9
Therefore 21 giants can generate 3.9 gigawatts.