Introduction
Sunita’s mother has 8 bananas. Sunita has to go for a picnic with her friends. She wants to carry 10 bananas with her. Can her mother give 10 bananas to her?
She does not have enough, so she borrows
After giving 10 bananas to Sunita, how many bananas are left with her mother?
Can we say that she has zero bananas? She has no bananas with her, but has to return two to her neighbour. So when she gets some more bananas, say 6, she will return
Ronald goes to the market to purchase a pen. He has only Rs 12 with him but the pen costs Rs 15. The shopkeeper writes Rs 3 as due amount from him. He writes Rs 3 in his diary to remember Ronald’s debit. But how would he remember whether Rs 3 has to be given or has to be taken from Ronald?
Can he express this debit by some colour or sign?
Ruchika and Salma are playing a game using a number strip which is marked from 0 to 25 at equal intervals
To begin with, both of them placed a coloured token at the zero mark. Two coloured dice are placed in a bag and are taken out by them one by one. If the dice is red in colour, the token is moved forward as per the number shown on throwing this dice. If it is blue, the token is moved backward as per the number shown when this dice is thrown.
salma.
The dice are put back into the bag after each move so that both of them have equal chance of getting either dice. The one who reaches the 25th mark first is the winner.
They play the game. Ruchika gets the red dice and gets four on the dice after throwing it. She, thus, moves the token to mark four on the strip. Salma also happens to take out the red dice and wins 3 points and, thus, moves her token to number 3.
number strip.
In the second attempt, Ruchika secures three points with the red dice and Salma gets 4 points but with the blue dice.
Where do you think both of them should place their token after the second attempt?
Ruchika moves
So, reaches 4 + 3 i.e. the
Whereas Salma placed her token at zero position. But Ruchika objected saying she should be behind zero. Salma agreed. But there is nothing behind zero. What can they do?
Salma and Ruchika then extended the strip on the other side. They used a blue strip on the other side.
Now, Salma suggested that she is one mark behind zero, so it can be marked as blue
If the token is at blue one, then the position behind blue one is blue two.
Similarly, blue three is behind blue two. In this way they decided to move backward. Another day while playing they could not find blue paper, so Ruchika said, let us use a sign on the other side as we are moving in opposite direction. So you see we need to use a sign going for numbers less than
The sign that is used is the placement of a minus sign attached to the number. This indicates that numbers with a negative sign are less than
Question: Suppose David and Mohan have started walking from zero position in opposite directions. Let the steps to the right of zero be represented by ‘+’ sign and to the left of zero represented by ‘–’ sign.
If Mohan moves 5 steps to the right of zero it can be represented as +5 and if David moves 5 steps to the left of zero it can be represented as –5. Now represent the following positions with + or – sign :
Who follows me?
We have seen from the previous examples that a movement to the right is made if the number by which we have to move is
If a movement of only
Write the succeeding number of the following :
A movement to the left is made if the number by which the token has to move is
If a movement of only 1 is made to the
Now write the preceding number of the following :
Tag me with a sign
We have seen that some numbers carry a minus sign.
For example, if we want to show Ronald’s due amount to the shopkeeper we would write it as
Profit and Loss
Following is an account of a shopkeeper which shows profit and loss from the sale of certain items.
Since profit and loss are opposite situations and if profit is represented by
The height of a place above sea level is denoted by a
Height becomes lesser and lesser as we go lower and lower.
Thus, below the surface of the sea level we can denote the height by a
If earnings are represented by ‘+’ sign, then the spendings may be shown by a ‘–’ sign.
Similarly, temperature above 0°C is denoted a
For example, the temperature of a place 10° below 0°C is written as
Choose the aprropriate option