80 budding DJ's attend a club to practice their skills each week.
60% if those attending the club practice scratch mixing, the rest practice beat mixing.
Of those practising scratch mixing, 15 are female.
Of those practising beat mixing, 12 are male.
Start with the total frequency bubble at the start of the frequency tree - 80.
Work out 60% of 80 to find the frequency for scratch mixing.
Work your way through the rest of the tree.
beat:
We are given that 15 of the scratch mixers are female and that 12 of the beat mixers are male.
scratch and female:
beat and female:
Now we have all the values, we can complete the frequency tree.
Quick check on bubble totals: 48 + 32 = 80, 33 + 15 + 12 + 20 = 80.