My Maths and I: WAEC Mathematics Question 2015 ( Essay Question Four 4a )

WAEC Mathematics Question 2015 ( Essay Question Four 4a )

May 21, 2020

By Kings

WAEC Mathematics 2015, WAEC Mathematics 2015 Essay

4a. By how much is the sum of less than 7?

SOLUTION

Let the sum of $3\tfrac{2}{3}$ and $2\tfrac{1}{5}$ be k.

And how much is the sum of $3\tfrac{2}{3}$ and $2\tfrac{1}{5}$ less than 7 be 7-k.

Hence; The sum of $3\tfrac{2}{3}$ and $2\tfrac{1}{5}$ which is k will be expressed as

$k = 3\tfrac{2}{3} + 2\tfrac{1}{5}$

Converting the mixed fractions to improper fraction, we have

$k = \frac{(3\times 3)+2}{3}+\frac{(5\times 2)+1}{5}$

$k = \frac{9+2}{3}+\frac{10+1}{5}$

$k = \frac{11}{3}+\frac{11}{5}$

The LCM of 3 and 5 is 15

$k = \frac{(5\times 11)+(3\times 11)}{15}$

$k = \frac{55+33}{15}$

$k = \frac{88}{15}$

Therefore, how much sum of $3\tfrac{2}{3}$ and $2\tfrac{1}{5}$ is less than 7 which is expressed as 7-k becomes $7-\frac{88}{15}$

$\frac{7}{1}-\frac{88}{15}$

The LCM of 1 and 15 = 15

$= \frac{(15\times 7)-(1\times 88)}{15}$

$= \frac{105-88}{15}$

$= \frac{17}{15}$

Simplifying further;

$= \frac{15+2}{15}$

$= \frac{15}{15}+\frac{2}{15}$

$= 1+\frac{2}{15}$

$= 1\frac{2}{15}$ ANSWER

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