In school D, total number of children who didn’t used any of the stationary items are 115 and the ratio of girls who used the stationary items to that who didn’t used any of the items are 4:7 respectively. If 40 boys used both the items, then find the number of boys who didn’t use any of the items.

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