BECE Mathematics 2010 Paper

Before you can express as a percentage, both must be in the same unit. Is either you change the minutes to hours or hours to minutes.Change the seconds to minutes. 60 seconds make 1 minute. Hence 30 seconds is half ( $\frac{1}{2}$ ) minutes.$7\,\text{min}\,30\,\text{sec}=7\,\text{minutes}+\frac{1}{2}\,\text{minutes.}$$7\,\text{min}\,30\,\text{sec}=7\,\frac{1}{2}\,\text{minutes}$$7\,\text{min}\,30\,\text{sec}=\frac{2 \times 7 + 1}{2}\,\text{minutes}$$7\,\text{min}\,30\,\text{sec}=\frac{14+1}{2}\,\text{minutes}$$7\,\text{min}\,30\,\text{sec}=\frac{15}{2}\,\text{minutes}$ $\text{Percentage} = \frac{\text{Number}}{\text{Total}} \times 100 \%$$1 \text{ hour } = 60 \text{ minutes}$$\text{Percentage} = \frac{15}{2} \text{ minutes} \div 60 \text{ minutes} \times 100 \%$The minutes cancel each other.$\text{Percentage} = \frac{15}{2} \div 60 \times 100 \%$Every number/letter is being divided by 1 but not written.$60 = \frac{60}{1}$ $\text{Percentage} = \frac{15}{2} \div \frac{60}{1} \times 100 \%$Reciprocate the fraction (numerator becomes denominator and denominator becomes numerator) at the right and change the division $\div$ to multiplication ( x ) sign.$\text{Percentage} = \frac{15}{2} \times \frac{1}{60} \times 100 \%$Note: 15 divides itself 1 and 60, 4 times.$\text{Percentage} = \frac{1}{2} \times \frac{1}{4} \times 100 \%$Note: 4 divides itself 1 and 100, 25 times.Percentage $= \frac{1}{2} \times 25 \%$Percentage $= \frac{1 \times 25 \%}{2}$Percentage $= \frac{25 \%}{2}$Percentage = 12.5\%