An electronics manufacturer recorded the battery life of some different models of mobile phone.
They have displayed some of their results in the incomplete histogram and frequency table below.
Use this information to work out the missing value that completes the frequency table.
Frequency density
15
20
Battery life, (hours)
Frequency
15 <20
130
20 <22
28
22 <28
300
28 <30
25 30
35
Battery life (hours)