Page 12 - Start Up Mathematics_7

(b) Number of jumps required to reach back can be calculated as:
4 – 2 + 4 – 2 + 4 = 8
i.e., he has to jump 5 times to reach back.
(c) The moves in (i) and (ii) have been shown in (a) and (b) above. The sum 8 in
(ii) represents going up by 8 steps.

EXERCISE 1.1

1. Find the sum of the following integers:
(a) 8 and 21 (b) 25 and –13 (c) –16 and –8 (d) 35 and –11

2. Evaluate the following either by direct method or by using a number line:
(a) 3 + (–2) (b) –3 + 4 + (–7) (c) 8 – (–2) – 3 (d) 7 + (–5) + 1

3. Represent the following as integers with appropriate sign:
(a) Temperature of Leh is 13ºC below 0ºC. (b) A well is 130 m deep.

(c) The height of TV tower is 90 m. (d) A gain of ` 50,000
4. Complete the following table:

+ –6 –3 –2 –1 0 2 5 7
1

3
8

–1
–5

5. Arrange the following integers in descending order:
(a) –45, 34, –890, 219 (b) 678, –980, 432, –675

6. The midnight temperature of Delhi in the month of December was 10ºC. It dropped by 4ºC
in the next three hours. What was the temperature after 3 hours?
7. Morning temperature on a particular day in Chandigarh in the month of October was recorded
as 13.5ºC. However, by afternoon it rose by 7ºC. What was the temperature recorded in the
afternoon?
8. A plane is flying at a height of 5,850 m. A submarine is floating at a depth of 700 m below
the sea level exactly below the plane at a particular time. What is the distance between the
plane and the submarine?
9. In a quiz, 2 positive marks are allotted for each correct answer and –1 for
each incorrect answer. In four rounds of quiz, Reshma scored 45, –34, 40
and –36 marks and Radha scored –42, –12, 28 and 38 marks. Who scored
more marks?
10. A monkey is trying to climb a pole measuring 15 m, which is greased. He
tries to climb 3 m and slips down 2 m every time. In how many attempts
will the monkey be able to climb 10 m of the pole?

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