Example 2 - Chapter 4 Class 7 - Expressions using Letter-Numbers (Ganita Prakash)

Transcript

Example 2 Parthiv is making matchstick patterns. He repeatedly places Ls next to each other. Each L has two matchsticks as shown in Figure 4.2. How many matchsticks are needed to make 5 L’s? How many matchsticks are needed to make 7 L’s? How many matchsticks are needed to make 45 L’s? Now, what is the relation between the number of L’s and the number of sticks? We observe that 1 L require 2 matchsticks 2 L’s require 4 matchsticks 3 L’s require 6 matchsticks 4 L’s require 8 matchsticks And so on So, this is a pattern Number of matchsticks = 2 × Number of L’s Writing n = number of L’s Therefore, Number of matchsticks = 2n Now, we can answer our questions How many matchsticks are needed to make 5 L’s? Number of matchsticks = 2 × 5 = 10 How many matchsticks are needed to make 7 L’s? Number of matchsticks = 2 × 7 = 14 How many matchsticks are needed to make 45 L’s? Number of matchsticks = 2 × 45 = 90 Now, what is the relation between the number of L’s and the number of sticks? Number of matchsticks = 2n