Ncert Solutions For Class 7 Maths Ex 12.4

Ncert Solutions For Class 7 Maths Chapter 12 Ex 12.4

Q1: Observe the pattern made from the line segment, which are of equal length which are found in display of calculators and digital speedometer: If n is the number of digits, and the number of required segments to form the digit n is given by the algebraic expression on the right of the digit. So how many segments are required to form 5,10,100 digits of the kind .

Sol:

 

S.no Symbols Digit’s number Pattern Formulae No. of segments
(i)  

5
10
100
5n+1  

26
51
501
(ii)  

5
10
100
3n+1  

16
31
301
(iii)  

5
10
100
5n+2  

27
52
502

 

(i) 5n+1

Putting n=5,          5×5+1=25+1=26

Putting n=10,        5×10+1=50+1=51

Putting n=100,       5×100+1=500+1=501

 

(ii) 3n+1

Putting n=5,          3×5+1=15+1=16

Putting n=10,        3×10+1=30+1=31

Putting n=100,        3×100+1=300+1=301

 

(iii) 5n+2

Putting n=5,          5×5+2=25+2=27

Putting n=10,        5×10+2=50+1=52

Putting n=100,       5×100+2=500+1=502

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