Answer
Tallest: $230,000,000,000 = 2.3 \times 10^{11}$
Shortest: $150,000,000,000 = 1.5 \times 10^{11}$
Work Step by Step
Using eye to judge.
The tallest bar is slightly greater than half-way between 200 and 250, so it is about 230 billion.
$230,000,000,000 = 2.3 \times 10^{11}$
The shortest bar is touching 150 billion.
$150,000,000,000 = 1.5 \times 10^{11}$