Page 28 - Start Up Mathematics_7

(a) Between 0° and 12° (b) Between –6° and 12° (c) Above 15°

INJ-T20

INJ-F308

INJ-58R

–9° –6° –3° 0° 3° 6° 9° 12° 15° 18° 21° 24° 27° 30°
Temperature in °C

Values and Life Skills

1. An elevator descends into a mine shaft at the rate of 9 m per min. If the descent starts from
20 m above the ground level, how long will it take to reach –250 m? Have you ever been in

an elevator? What you will do if you are stuck in an elevator?
2. A chair costs ` 120. Peter bought 30 chairs. By mistake the shopkeeper charged ` 10 less per
chair. To be fair to all, find whether Peter had to pay or receive the money. What is the extra

amount? What will you do if by mistake, shopkeeper returns you extra money?
Some NCERT Textbook Questions

1. Use the sign of >, < or = in the box to make the statements true.
(a) (–8) + (–4) (–8) – (–4)

(b) (–3) + 7 – (19) 15 – 8 + (–9)

(c) 23 – 41 + 11 23 – 41 – 11

(d) 39 + (–24) – (15) 36 + (–52) – (–36)
(e) –231 + 79 + 51 –399 + 159 + 81

2. (a) Write a pair of negative integers whose difference gives 8.
(b) Write a negative integer and a positive integer whose sum is –5.
(c) Write a negative integer and a positive integer whose difference is –3.

3. In a quiz, team A scored –40, 10, 0 and team B scored 10, 0 –40 in three successive rounds.
Which team scored more? Can we say that we can add integers in any order?

4. Verify the following:
(a) 18 × [7 + (–3)] = [18 × 7] + [18 × (–3)]

(b) (–21) × [(–4) + (–6)] = [(–21) × (–4)] + [(–21) × (–6)]
5. A cement company earns a profit of ` 8 per bag of white cement sold and a loss of ` 5 per
bag of grey cement sold.
(a) The company sells 3,000 bags of white cement and 5,000 bags of grey cement in a month.
What is its profit or loss?
(b) What is the number of white cement bags it must sell to have neither profit nor loss, if
the number of grey bags sold is 6,400 bags.

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