Exercise 1.4 Maths Solutions, NCERT Maths solutions for class 7th, Questions and answers of NCERT class 7th Mathematics, NCERT Class 7th Mathematics Chapter 1 – Integers Solutions Exercise 1.4 Solutions, Class 7th maths solutions.
Please find the detailed Solutions for class 7th Maths chapter 1 exercise 1.1, you can check all the solutions from here chapter wise
NCERT Class 7th Mathematics Chapter 1 – Integer Solutions Exercise 1.4 Solutions
Exercise 1.4
1. Evaluate each of the following:
(a) (–30) ÷ 10
(b) 50 ÷ (–5)
(c) (–36) ÷ (–9)
(d) (– 49) ÷ (49)
(e) 13 ÷ [(–2) + 1]
(f) 0 ÷ (–12)
(g) (–31) ÷ [(–30) + (–1)]
(h) [(–36) ÷ 12] ÷ 3 (i) [(– 6) + 5)] ÷ [(–2) + 1]
Ans. (a) (–30) ÷ 10 = -3
(b) 50 ÷ (–5) = -10
(c) (–36) ÷ (–9) = 4
(d) (– 49) ÷ (49) = -1
(e) 13 ÷ [(–2) + 1] = 13 ÷ (-1) = -13
(f) 0 ÷ (–12) = 0
(g) (–31) ÷ [(–30) + (–1)]= (-31) ÷ (-31) = 1
(h) [(–36) ÷ 12] ÷ 3 = 3 ÷ 3 = 1
(i) [(– 6) + 5)] ÷ [(–2) + 1] = (-1) ÷ (-1) = 1
2. Verify that a ÷ (b + c) ≠ (a ÷ b) + (a ÷ c) for each of the following values of a, b and c.
(a) a = 12, b = – 4, c = 2 (b) a = (–10), b = 1, c = 1
Ans. (a) a = 12, b = – 4, c = 2
a ÷ (b + c) = 12 ÷ [(-4) + 2]= 12 ÷ (-2) = -6
(a ÷ b) + (a ÷ c) = (12 ÷ (-4)) + (12 ÷ 2) = -3 + 6 = 3
Therefore a ÷ (b + c) ≠ (a ÷ b) + (a ÷ c).
(b) a = (–10), b = 1, c = 1
a ÷ (b + c) = (-10) ÷ (1 + 1) = (-10) ÷ 2 = -5
(a ÷ b) + (a ÷ c) = ( (-10) ÷ 1) + ( (-10) ÷ 1) = (-10) + (-10) = -10 – 10 = -20
Therefore a ÷ (b + c) ≠ (a ÷ b) + (a ÷ c).
3. Fill in the blanks:
(a) 369 ÷ _____ = 369
(b) (–75) ÷ _____ = –1
(c) (–206) ÷ _____ = 1
(d) – 87 ÷ _____ = 87
(e) _____ ÷ 1 = – 87
(f) _____ ÷ 48 = –1
(g) 20 ÷ _____ = –2
(h) _____ ÷ (4) = –3
Ans. (a) 369 ÷ 1= 369
(b) (–75) ÷ 75 = –1
(c) (–206) ÷ (-206) = 1
(d) – 87 ÷ (-1) = 87
(e) (-87) ÷ 1 = – 87
(f) (-48) ÷ 48 = –1
(g) 20 ÷ (-10) = –2
(h) (-12) ÷ (4) = –3
4. Write five pairs of integers (a, b) such that a ÷ b = –3. One such pair is (6, –2) because 6 ÷ (–2) = (–3).
Ans. (12, -4), (-9, 3), (-15, 5), (18, -6), (-21, 7).
5. The temperature at 12 noon was 10°C above zero. If it decreases at the rate of 2°C per hour until midnight, at what time would the temperature be 8°C below zero? What would be the temperature at mid-night?
Ans. The temperature at 12 noon = 10°C
The temperature decreases 2°C = 1 hour
The temperature decreases 1°C = ½ hour
The temperature decreases 18°C = ½ x 18 = 9 hours
Total time = 12 noon + 9 hr = 21 hours = 9 pm
Thus, at 9pm the temperature would be -8°C.
6. In a class test (+ 3) marks are given for every correct answer and (–2) marks are given for every incorrect answer and no marks for not attempting any question.
(i) Radhika scored 20 marks. If she has got 12 correct answers, how many questions has she attempted incorrectly?
(ii) Mohini scores –5 marks in this test, though she has got 7 correct answers. How many questions has she attempted incorrectly?
Ans.Given:
Marks obtained for one correct answer = 3
Marks obtained for one incorrect answer = -2
i) Marks obtained for 12 correct answers = 3 x 12 = 36
Radhika scored 20 marks.
Therefore, marks obtained for incorrect answers = 20 – 36 = -16
Number of incorrect answers = (-16)÷(-2) = 8
Thus, Radhika has attempted 8 incorrect questions.
ii) Marks given for seven correct answers = 3 x 7 = 21
Mohini scored -5.
Marks obtained for incorrect answers = -5 -21 = -26
Number of incorrect answers = (-26)÷(-2) = 13
Thus, Mohini attempted 13 incorrect questions.
7. An elevator descends into a mine shaft at the rate of 6 m/min. If the descent starts from 10 m above the ground level, how long will it take to reach – 350 m.
Ans. Total distance covered by mine shaft = 10 m – (-350 m) = 10 + 350 = 360 m
According to the question, time taken to cover a distance of 6m = 1 min
So, time taken to cover a distance of 1 m = 1/6 min
Therefore, time taken to cover a distance of 360 m = 1/6×360
= 60 minutes
= 1 hour
Thus, the elevator will reach -350 m from 10 m in one hour.
You can find the solutions for previous exercise from here
You can find solution for whole chapter here –
