CBSE students can refer to NCERT Solutions for Class 7 Maths Chapter 12 Algebraic Expressions Ex 12.4 Textbook Questions and Answers are provided by experts in order to help students secure good marks in exams.
Class 7 Maths NCERT Solutions Chapter 12 Algebraic Expressions Ex 12.4
Question 1.
Observe the patterns of digits made from line segments of equal length. You will find such segmented digits on the display of electronic watches or calculators. If the number of digits formed is taken to be n, the number of segments required to form n digits is given by the algebraic expression appearing on the right of each pattern. How many segments are required to form 5,10,100 digits of the kind?
(a)
Solution:
We know that the number of segments required to form n digits of the kind 
is (5n + 1).Therefore, to form 5,10,100 digits of above kind the number of segments required are (5 × 5 + 1) = 25 + 1 = 26, (5 × 10 + 1) = 50 + 1 = 51 and t (5 × 100 + 1) = 500 + 1 = 501, respectively.
(b)
Solution:
(b) We know that the number of segments required to form n digits of the kind
is (3n + 1). Therefore, to form 5, 10, 100 digits of above kind the number of segments required are (3 × 5 + 1) = 15 + 1 =16, (3 × 10 +1) = 30 + 1 = 31 and (3 × 100 +1) = 300 +1 = 301 respectively.
(c)
Solution:
We know that the number of segments required to form n digits of the kind 
is (5n + 2). Therefore, to form 5, 10, 100 digits of above kind the number of segments required are (5 × 5 + 2) = 25 + 2 = 27, (5 × 10 + 2) = 50 + 2 = 52 and (5 × 100 + 2) = 500 + 2 = 502 respectively.
Question 2.
Use the given algebraic expression to complete the table of number patterns :
Solution:
The completed table of number patterns is as given below :
