Example 3 (Page 59) - Chapter 3 Class 8 - Proportional Reasoning-2 (Ganita Prakash II)

Transcript

Example 3 (Page 59) For some construction, 110 units of concrete are needed. How many units of cement, sand, and gravel are needed if these are to be mixed in the ratio 1 : 1.5 : 3?Given ratio 1 : 1.5 : 3 First, we add up Total Parts Total parts = 1 + 1.5 + 3 = 5.5 Thus, we have 5.5 parts of concrete Since we need 110 units total, we find out how much is 1 part worth Value of 1 part = (𝑇𝑜𝑡𝑎𝑙 𝑢𝑛𝑖𝑡𝑠)/(𝑇𝑜𝑡𝑎𝑙 𝑝𝑎𝑟𝑡𝑠) = 𝟏𝟏𝟎/(𝟓.𝟓) = 110/(55/10) = 110/55 × 10 = 20 So, we multiply each part by 20 Thus, units of cement, sand and gravel are Cement = 1 × 20 = 20 Sand = 1.5 × 20 = 15/10 × 20 = 15 × 2 = 30 Gravel = 3 × 20 = 60 Therefore, we need 20 units of cement, 30 units of sand, and 60 units of gravel to make the concrete.