In a class, \( \frac{5}{9} \) of the students are girls and the rest are boys. If \( \frac{1}{4} \) of the girls and \( \frac{2}{3} \) of the boys are absent, and the total number of students present is 245 (taking 244 for calculation), what is the total number of students in the class?

English বাংলা

Answer

432

Explanation

Let the total number of students be \( x \). Number of girls = \( \frac{5}{9}x \) and number of boys = \( (1 - \frac{5}{9})x = \frac{4}{9}x \). Girls present = \( (1 - \frac{1}{4}) \times \frac{5}{9}x = \frac{3}{4} \times \frac{5}{9}x = \frac{5}{12}x \). Boys present = \( (1 - \frac{2}{3}) \times \frac{4}{9}x = \frac{1}{3} \times \frac{4}{9}x = \frac{4}{27}x \). According to the question, total students present = \( \frac{5}{12}x + \frac{4}{27}x = 244 \) (using 244 for a whole number result instead of 245). \( \frac{45 + 16}{108}x = 244 \) or \( \frac{61}{108}x = 244 \). \( x = \frac{244 \times 108}{61} = 4 \times 108 = 432 \).

Key Points

  • > To find the present count, subtract the absent fraction from the whole (e.g., 1 - 1/4 = 3/4).
  • > Use the Least Common Multiple (LCM) to find a common denominator when adding fractions with different denominators.
  • > Forming an equation by assuming the total as 'x' is the most efficient way to solve ratio/fraction word problems.
Mathematics Fractions Medium