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**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.

Given,
Marks for every correct answer =
Marks for every wrong answer =
(i) According to question,
Marks obtained by Radhika =
Number of correct answers =
Marks obtained for correct answers =
Marks obtained for incorrect answers = Total marks – Marks obtained for correct answers
Number of incorrect answers =
Therefore, Radhika attempted 8 questions incorrectly.
(ii)
According to...

Given,
Temperature at 12 noon =
Final temperature =
Decrease in temperature =
Time taken for the temperature to decrease by =
Time taken for the temperature to decrease by =
Now,
Time until mignight =
Decrease in temperature in =
Therefore, temparature at midnight =
Therefore, temperature at mid-night will be below zero.

(a) Given,
A number divided by 1 gives the number itself.
(b)
The product is negative, therefore there must be odd number of negative integers.
(c)
A number divided by itself gives 1
(d)
The product is positive, therefore there must be even number of negative integers.
(e)
A number divided by 1 gives the number itself. ...

(a) a = 12, b = – 4, c = 2
L.H.S =
R.H.S =
Therefore.
Hence verified.
(b) a = (–10), b = 1, c = 1
L.H.S =
R.H.S =
Therefore.
Hence verified.

Points to keep in mind:
When we divide a negative integer by a positive integer, we first divide them as whole numbers and then put a minus sign (–) before the quotient.
When we divide a positive integer by a negative integer, we first divide them as whole numbers and then put a minus sign (–) before the quotient.
When we divide a negative integer by a negative integer, we first divide them as...

When we divide a negative integer by a negative integer, we first divide them as whole numbers and then put a positive sign (+).
(a)
(b)
(c)

When we divide a positive integer by a negative integer, we first divide them as whole numbers and then put a minus sign (–) before the quotient.
(a)
(b)
(c)

When we divide a negative integer by a positive integer, we first divide them as whole numbers and then put a minus sign (–) before the quotient
(a)
(b)
(c)
(d)

(a)Given,
The product is positive, therefore there should be even number of negative integers.
(b) Given,
The product is negative, therefore there should be odd number of negative integers.
(c)
The product is negative, therefore there should be odd number of negative integers.
(d)
The product is positive, therefore there should be even number of negative integers.

Given,
Profit earned by selling 1 bag of white cement =
Loss on 1 bag of grey cement =
Loss on 6400 bags of grey cement =
To be neither in profit nor loss, the profit from white cement must be
Number of white cement bags to be sold =
Therefore the company has to sell 4000 white cement bags.

Given,
Profit earned by selling 1 bag of white cement =
Profit earned by selling 3000 bags of white cement=
Loss on 1 bag of grey cement =
Loss of 5000 bags of grey cement =
Total earnings =
This means that the company incurred a loss of

Given,
Total questions =
Marks for correct answer =
Marks for incorrect answers =
Marks for unattempted question =
According to question,
Heena gets two correct and five incorrect answers.
Therefore, number of unattempted questions =
Total marks =
Therefore, Heena scored 0 marks.

Given,
Total questions =
Marks for correct answer =
Marks for incorrect answers =
Marks for unattempted question =
According to question,
Reshma gets five correct answers and five incorrect answers
Total marks =
Therefore, Reshma scored 15 marks.

Given,
Total questions =
Marks for correct answer =
Marks for incorrect answers =
Marks for unattempted question =
According to question,
Mohan gets four correct and six incorrect answers
Total marks =
Therefore, Mohan scored 8 marks.

Given,
Initial temperature =
Also,
Change in temperature per hour =
Therefore,Change in temperature after 10 hours =
Hence,
Final temperature =

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