Samacheer Kalvi 7th Maths Solutions Term 1 Chapter 1 Number System Ex 1.4

Samacheer Kalvi 7th Maths Solutions Term 1 Chapter 1 Number System Ex 1.4

Tamilnadu Samacheer Kalvi 7th Maths Solutions Term 1 Chapter 1 Number System Ex 1.4

Question 1.
Fill in the blanks.
(i) (-40) ÷ ___ =40
(ii) 25 ÷ ____ = -5
(iii) ____ ÷ (-4) = 9
(iv) (-62) ÷ (-62) = ____
Solution:
(i) -1
(ii) -5
(iii) -36
(iv) 1

Question 2.
Say True or False:
(i) (-30) ÷ (-6) = -6
(ii) (-64) ÷ (-64) is 0
Solution:
(i) False
(ii) False

Question 3.
Find the values of the following.
(i) (-75) ÷ 5
(ii) (-100) ÷ (-20)
(iii) 45 ÷ (-9)
(iv) (-82) ÷ 82
Solution:
(i) −75/5 = -15
(ii) −100/−20 = 5
(iii) 45/−9 = -5
(iv) −82/82 = -1

Question 4.
The product of two integers is -135. If one number is -15. Find the other integer.
Solution:
Given the product of two integers = -135
One of them = -15
∴ -15 × Another number = -135
Other number = −135/−15 = 9
∴ The other number = 9.

Question 5.
In 8 hours duration, with uniform decrease in temperature, the temperature dropped 24°C. How many degrees did the temperature drop each hour?
Solution:
In 8 hours the drop in temperature = 24
In 1 hour the drop in temperature = 24/8 = 3°
The temperature dropped 3°C every hour.

Question 6.
An elevator descends into a mine shaft at the rate of 5 m/min. If the descent starts from 15 m above the ground level, how long will it take to reach -250 m?
Solution:
The elevator’s position = 15 m above ground level = +15 m
It should reach = -250 m
The distance to be travelled = 15 – (-250) m = 15 + (+250) m 265 m
Time taken to descend 5 m = 1 min
∴ Time required to descend 265 m = 24/8 = 53 min

Question 7.
A person lost 4800 calories in 30 days. If the calory loss is uniform, calculate the loss of calory per day.
Solution:
Loss of calory in 30 days = 4800
∴ Loss of calory in 1 day = 4800/30 = 160 calories
∴ 160 calories lost per day.

Question 8.
Given 168 × 32 = 5376 then fined (-5376) ÷ (-32).
Solution:
Given 168 × 32 = 5376
∴ 5376/32 = 168
Also, −5376/−32 = 168

Question 9.
How many -4’s are there is (-20)?
Solution:
Number of -4’s in (-20) = −20/−4 = 5

Question 10.
(-400) divided into 10 equal parts gives ____
Solution:
−400/10 = -4

Objective Type Questions

Question 11.
Which of the following does not represent an integer?
(i) 0 ÷ (-7)
(ii) 20 ÷ (-4)
(iii) (-9) ÷ 3
(iv) 12 ÷ 5
Solution:
(iv) 12 ÷ 5

Question 12.
(-16) ÷ 4 is the same as
(i) -(-16 ÷ -4)
(ii) -(16) ÷ (-4)
(iii) 16 ÷ (-4)
(iv) -4 ÷ -16
Solution:
(iii) 16 ÷ (-4)

Question 13.
(-200) ÷ 10 is
(i) 20
(ii) -20
(iii) -190
(iv) 210
Solution:
(ii) 20

Question 14.
The set of integers is not closed under
(i) Addition
(ii) Subtraction
(iii) Multiplication
(iv) Division
Solution:
(iv) Division