NCTB Class 7 Math Chapter One Exercise 1.2 Solution by Math Expert. Bangladesh Board Class 7 Math Solution Chapter 1”Rational & Irrational Numbers” Exercise 1.2 Solution.
|”Rational & Irrational Numbers”|
(3) A rational number is —
Solution:- (d) (i), (ii), (iii) are correct.
The difference of squares of two consecutive numbers is 19.
Answer to question no. 4 and 5 following the information.
(4) If one number is 10, what is the other number?
Solution:- Two consecutive number is 9, 10 other number is = (c) 9.
(5) What is the sum total of squares of the two numbers?
Solution:- (10)2+ (9)2 = 100+ 81
(c) = 181.
(6) Which of the following is the square root of 0.01?
Solution:- √ 0.01= 0.1 (b)
(7) If the digit in unit place of a number is either 2 or 8, the digit in unit place of its square will be —
Solution:- (c) 6.
(8) By which number the multiplication or division of 3×7 x5x 7×3 will be perfect square number?
Solution:- 3×7 x5x 7×3
= (3×3) x (7×7) x 5
Therefore, the number is (b) 5 (answer).
(9) Which one of the irrational number?
Solution:- The irrational number is = (a) √2.
(10) (a) How much money did he spend to buy the plants?
Solution:- Total money speed = (12×595)= 7140 Rs (Taka).
(17) Each member of a cooperative society subscribes 20 times the number of the members in Takas. The total amount raised being TK.20480, find the number of members of the society.
Solution:- Let, the number of member is a
Therefore, 1 —- a x 20
Therefore, a —- a x a x 20
= 20 a2.
Therefore, 20 a2.= 20480 (Total amount).
=> a2 = 20480/20
=> a = √ 1024 = 32
Therefore, The number of member of society is 32.
(20) Labours were employed to reap paddy from a paddy field. The daily wage of each labour is 10 times of their numbers. If the total daily wage is TK.6250, find the number of the labours.
Solution:- Let, the number of labour x.
Therefore, wages = xX10 = 10x Rs.
Therefore, = x X 10x = 10x2 Rs.
Therefore, 10x2 = 6250
=> x2 = 625
Therefore, The number of labour is 25.
(21) The difference of squares of two consecutive number is 37. Find the two number.
Solution:- Let, the number are x & x+1
Therefore, Square of numbers = and (x+1)2
Therefore, (x+1)2 – x2 = 37
=> x2+ 2x+1- x2 = 37
=> 2x +1= 37
=> 2x = 37-1
=> x = 36/2
Number are 18, 19 (Answer) and another number is = (18+1) = 19.
Let, the number, x & x+1
Therefore Difference of square of the number
= (x+1)2 – x2
= x2+ 2x+1- x2
Therefore, x=2 ; 2×2+1= 5
X=3 ; 2x3x1= 7
X=4; 2×4+1 = 9 (Square number)
Therefore, One number is 4 and another number (4+1) = 5.
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