Question

I'm so confused please help

Answer 1

Answer:

84.3%

Step-by-step explanation:

Total frequency is the total area:

Add all the areas

To find each area:

Frequency density × class width

Total frequency:

40×10 + 30×10 + 25×20 + 15×5

= 1275

Less than 40:

Bar 1 + Bar 2 + some part of Bar 3

40×10 + 30×10 + 25×15

= 1075

Percentage (<40) = 1075/1275 × 100

= 4300/51

= 84.31372549%

Answer 2

I'm confused too and I'm supposed to be an expert.  I'm not entirely sure what frequency density is.  We'll just treat this as a histogram.

Let's assume each five minute interval gives a value equal to or proportional to the number of people that finished in that interval.

From 0 to 50 we have 10 intervals; let's just make this into a table

0-5  0

5-10 40

10-15 40

15-20 30

20-25 30

25-30 25

30-35 25

35-40 25

40-45 25  

45-50 15

From 0 to 40 that adds up to

0+40+40+30+30+25+25+25 = 215

From 0 to 50 that's

215+25+15 = 255

The fraction less than 40 is 215/255 = 43/51 ≈ .843

Answer: 84.3%