NCERT Class 7 Solutions: Integers (Chapter 1) Exercise 1.1 – Part 2
Q4 A plane is flying at the height of 5000 m above the sea level. At a particular point, it is exactly above a submarine floating 1200 m below the sea level. What is the vertical distance between them?
Solution:

Height of plane above the sea level

Floating a submarine below the sea level

∴The vertical distance between the plane and the submarine

Thus, the vertical distance between the plane and the submarine is 6200 m.
Q5 Mohan deposits Rs. 2,000 in his bank account and withdraws Rs. 1,642 from it, the next day. If withdrawal of amount from the account is represented by a negative integer, then how will you represent the amount deposited? Find the balance in Mohan’s accounts after the withdrawal?
Solution:


Withdrawal amount is represented as negative integer


Thus, the balance in Mohan’s account after withdrawal is Rs. 358.
Q6 Rita goes 20 km towards east from a point A to the point B. From B, she moves 30 km towards west along the same road. If the distance towards east is represented by a positive integer then, how will you represent the distance travelled towards west? By which integer will you represent her final position from A?
Solution:
Let Rita move on a number line with point A as zero.

According to the number line, Rita moves towards east is represented by a positive integer. In this case point B would be 20 (20 km).

Later she moves in opposite direction means Rita moves west, this will be represented by negative integer 30 (30 km).
Distance from A to B
Distance from B to C
Distance from A to C
Thus, Rita is at final position from A to C is 10 km.
Q7 In a magic square each row, column and diagonal have the same sum. Check which of the following is a magic square.
Solution:
Understand that the sum of a positive number and a negative number results in subtraction operation.

1^{st} magical square

Taking Rows

Taking 1^{st} row

Taking 2^{nd} row

Taking 3^{rd} row


Taking Columns

Taking 1^{st} column

Taking 2^{nd} column

Taking 3^{rd} column


Taking diagonals

Taking 1^{st} diagonal

Taking 2^{nd} diagonal
This box is not a magic square because all the sums are not equal.



2^{nd} ^{t} magical square

Taking Rows

Taking 1^{st} row

Taking 2^{nd} row

Taking 3^{rd} row


Taking Columns

Taking 1^{st} column

Taking 2^{nd} column

Taking 3^{rd} column


Taking diagonals

Taking 1^{st} diagonal

Taking 2^{nd} diagonal
This box is a magic square because all the sums are equal.
