Ratio, SM-Bank 031 Jordan has 4 times as many blue pencils as black pencils. Altogether he has 90 pencils. How many blue pencils does he have? (2 marks) --- 4 WORK AREA LINES (style=lined) --- Show Answers Only \(72\ \text{blue pencils}\) Show Worked Solution \(\text{Method 1}\) \(\text{Ratio of blue to black}=4:1\) \(\text{Total parts}=4+1=5\) \(\text{Fraction blue}=\dfrac{4}{5}\) \(\text{Number of blue pencils}=\dfrac{4}{5}\times 90=72\) \(\text{Method 2 (Advanced)}\) \(\text{Let}\ \ x = \text{the number of black pencils}\) \(\text{Then the number of blue pencils}=4x\) \(\text{Total pencils }= x + 4x\) \(=5x\) \(\rightarrow\ 5x\) \(= 90\) \(x\) \(=\dfrac{90}{5}= 18\) \(\therefore \ \text{The number of blue pencils}\) \(=90-18= 72\)