In school D, total number of children who didn’t used

Solution

In school A, Let total number of pencils and pens used be px and qx respectively. According to the question, => px – qx = 40 => 120 – qx = 40 => qx = 80 Ratio = px : qx = 120 : 80 = 3:2 Total number of pencils used = px = 120 Total number of pens used = qx = 80 In school B, Let total number of pencils and pens used be 3x and 2x respectively. According to the question, => 3x – 2x = 90 => x = 90 So, 3x = 270 and 2x = 180 Now, (m² + 45) = 270 => m² = 225 => m = 15 Total number of pencils used = 3x = 270 Total number of pens used = 2x = 180 In school C, Let total number of pencils and pens used be gx and hx respectively. According to the question, => gx = 8m – 70 => gx = (8 × 15) – 70 => gx = 50 So, hx = 50 – 20 = 30 Ratio = gx : hx = 50 : 30 = 5:3 Total number of pencils used = gx = 50 Total number of pens used = hx = 30 In school D, Let total number of pencils and pens used be tx and x respectively. According to the question, => tx = 75 So, tx – x = 50 => 75 - x = 50 => x = 25 Ratio = tx : x = 75 : 25 = 3:1 Total number of pencils used = tx = 75 Total number of pens used = x = 25 Total number of children who used both items = 75 + 25 = 100 Girls who used the both the items = 100 – 40 = 60 Girls who didn’t used any of the items = (7/4) × 60 = 105 Number of boys who didn’t use any of the items = 115 – 105 = 10