Question

paramecium contractile vacuole contractions
salt concentration outside paramecium\tcontractions per minute
very high\t2
high\t8
medium\t15
low\t22
very low\t30
if this data is shown in a bar graph, which description accurately represents the bars?
the graph has five bars of equal height.
the bars range from tallest for very high concentration to shortest for very low concentration.
the bar for very low concentration is twice the height of the bar for medium concentration.
the bar for very high concentration is five times the height of the bar for very low concentration.

Explanation:

Step1: Analyze the data

The contractions per minute for very high, high, medium, low and very low salt - concentrations are 2, 8, 15, 22 and 30 respectively.

Step2: Evaluate each option

• Option 1: The values are 2, 8, 15, 22, 30, so the bars are not of equal height.
• Option 2: The bar for very high concentration (2 contractions per minute) is the shortest and the bar for very low concentration (30 contractions per minute) is the tallest, so this option is incorrect.
• Option 3: The bar for very low concentration has 30 contractions per minute and the bar for medium concentration has 15 contractions per minute. Since $30 = 2\times15$, the bar for very low concentration is twice the height of the bar for medium concentration.
• Option 4: The bar for very high concentration has 2 contractions per minute and the bar for very low concentration has 30 contractions per minute. $30\div2 = 15$, not 5, so this option is incorrect.

Answer:

The bar for very low concentration is twice the height of the bar for medium concentration.