A histogram of puzzle-completion times has the following frequency densities.
time t (s)0≤t<3030≤t<6060≤t<9090≤t<120120≤t<150frequency density11486\begin{array}{c|ccccc}\text{time }t\text{ (s)}&0\leq t<30&30\leq t<60&60\leq t<90&90\leq t<120&120\leq t<150\\\hline\text{frequency density}&1&1&4&8&6\end{array}time t (s)frequency density0≤t<30130≤t<60160≤t<90490≤t<1208120≤t<1506
There are 120 people with completion time at least 150 seconds. Estimate the percentage who took less than 90 seconds.
105 exam-style questions on WJEC A Level Maths 2.2 Data presentation and interpretation, covering 2.2.1 Data presentation and interpretation, 2.2.2 Data presentation and interpretation, 2.2.3 Data presentation and interpretation, 2.2.4 Data presentation and interpretation, 2.2.5 Data presentation and interpretation, 2.2.6 Data presentation and interpretation, 2.2.7 Data presentation and interpretation, 2.2.8 Data presentation and interpretation, and 2.2 Data presentation and interpretation. Each one has a worked solution and a mark scheme showing where the marks go.