NCERT Solution class 7 Mathematics Exercise 1.1
Exercise – 1.1
Q1. Following number line shows the temperature in degree Celsius (^{0}C) at different places on a particular day .
SOLUTION:
(A) Observe this number line and write the temperature of the places marked on it .
SOLUTION:
By observing the number line we can find the temperature of the cities as follows,
Temperature at the lahulspiti is 8^{0}C
Temperature at the Srinagar is 2^{o}C
Temperature at the shimla is 5^{0}C
Temperature at the bengaluru is 22^{o}C
(B) What is the temperature difference between hottest and coldest places among the above?
SOLUTION:
From the number
The temperature at the hottest places bengaluru is 22^{0}C
The temperature at the coldest places lahulspiti 8^{0}C
Temperature difference between hottest and coldest place is = 22^{o}C – (8^{o}C)
= 22^{O}C + 8^{O}C
= 30^{0}C
(C) What is the temperature difference between lahulspiti and Srinagar ?
SOLUTION:
From the given number line
The temperature at the Srinagar is 2^{0}C
The temperature at the lahulspiti 8^{0}C
The temperature difference between lahulspiti and Srinagar is = 2^{0}C – (8^{0}C)
= 2^{O}C + 8^{O}C
= 6^{O}C
(D) Can we say temperature of Srinagar taken together is less than the the temperature at shimla ? Is it also less than the temperature at Srinagar ?
SOLUTION:
From the given number line
The temperature at Srinagar = 2^{0}C
The temperature at shimla = 5^{0}C
The temperature of srinagar and shimla taken together is = – 2^{o}C + 5^{O}C
= 3^{0}C
5^{0}C > 3^{0}C
So the temperature of Srinagar and shimla taken together is less than the temperature at shimla.
Then,
3^{0}C > 2^{0}C
No , the temperature of Srinagar and shimla taken together is not less than the temperature of Srinagar .
Q2. In a quiz positive marks are given for correct answers and negative marks given for the wrong answers . If JACK scores in five successive rounds were 25,5,10,15 and 10 ,what was his total at the end ?
ANS – FROM THE QUESTION
JACK SCORED IN FIVE SUCCESSIVE ROUNDS 25,5,10,15 and 10
2+(5) +(10)+15+10 = 35
Jack score a total at the end is 35
Q3. At Srinagar temperature was 5 degree Celsius on Monday and then it dropped by 2 degree Celsius on Tuesday .What was the temperature of Srinagar on Tuesday ? On Wednesday ,it rose by 4 degree Celsius . What was the temperature on this day ?
Ans From the question
The temperature on Monday at Srinagar 5degree Celsius
Temperature on Tuesday at Srinagar dropped by 2 degree Celsius =Temperature on Monday 2 degree Celsius
= 5 degree Celsius – 2 degree Celsius
= 7 degree Celsius
Temperature on Wednesday at Srinagar is rose by 4 degree Celsius = Temperature on Tuesday + 4 degree Celsius
=7 degree Celsius + 4 degree Celsius
=3 degree celsius
Thus the temperature on Tuesday and wednesday was 7 degree Celsius and 3 degree celsius respectively
Q4. A plane is flying at the height of 5000m above the sea level . At a particular point, it is exactly above a submarine floating 1200m below the sea level . What is the vertical distance between them ?
Ans – From the question ,
Plane is flying at the height =5000m
Depth of submarine = 1200m
The vertical height between plane and submarine =5000m(1200)m
=5000m+1200m
=6200m
Q5. Mohan deposit Rs 2000 in his bank account and withdraws Rs 1642 from it ,the next day . If withdrawl of amount from the account is represented by the negative integer ,then how will you represent the amount deposited? Find the balance in mohan account after the withdrawal .
Ans – Withdrawl of amount is represented by a negative integer .
Then, deposits of amount to the account is represented by a positive integer.
From the questions ,
Total amount deposited in bank account by the mohan = Rs= 2000
Total Amount withdrawn from the bank account by the mohan =1642
Balance in mohan account after the withdrawl =amount deposited +amount withdrawn =Rs2000 +(Rs 1642)
=Rs 2000 –Rs 1642
=Rs 358
Hence, the balance in Mohan account after the withdrawal is Rs 358
Q6. Rita goes 20 km towards east from a point A to the point B. From B ,she moves 30km towards west along the same road .If the distance towards east is represented by the positive integers then, how will you represent the distance travelled towards west ? By which integer will you represents her final position from A?
Ans – From the questions , it is given that
Then , distance travelled towards the west will be represented by a negative integer.
Rita travels a distance in east direction =20km
Rita travels a distance in west direction =30km
Distance travelled from A
= 20 + (30)
=2030
= 10Km
Hence ,we will represents the distance travelled by rita from point A by a negative integer , i.e. 10km
Q7. In a magic square each row , column and diagonal have the same sum. Check which of the following is a magic square.
5  1  4 
5  2  7 
0  3  3 

Ans – First we consider the square .
(i)By adding the numbers in each rows we get ,
=5 +(1)+(4)= 514
=55=0
= 5 +(2)+7 = 52+7
=7+7 =0
= 0+3+(3)=33 =0
By adding the numbers in each columns we get ,
= 5+(2)+(3)=523
=55=0
=4+(2)+0=42=6
Because sum of one diagonal is not equal to zero,
So,(i) is not a magic square
Now , we consider the square (ii)
By adding the numbers in each row we get ,
=1+(10)+0 =110+0=9
= (4) +(3)+(2)=432=9
By adding the numbers in each column we get,
= 1+(4)+(6)=146
=110=9
=(10)+(3)+4=103+4=13+4
=0+(2)+(7)=027
=9
By adding the numbers in diagonals we get ,
=1+(3)+(7)=137
=110=9
=0+(3)+(6)=036
=9
This (iii) square is a magic square ,because sum of each row each column and diagonal is equal to 9.
Q8.Verify a(b)=a+b for the following values of a and b.
(i) a=21 , b=18
Solution :
From the questions ,
A = 21 b=18
To verify a(b)=a+b
Let us take left hand side (LHS) = a(b)
=21(18)
=21+18
=39
Now right hand side (RHS)
=A+B
=21+18
=39
By comparing LHS and RHS
LHS=RHS
39=39
Hence, the value of a and b is verified.
(ii) a=118 , b=125
Solution : From the question ,
A=118 and b = 125
To verify a(b)=a+b
Let us take left hand side (LHS)=a(b)
=118(125)
=118+125
=243
Now , right hand side (RHS)=a+b
=118+125
=243
By comparing LHS and RHS
LHS=RHS
243=243
Hence , the value of a and b is verified