Page 127 - Start Up Mathematics_6

Example 21: Due to heavy snow, the temperature in Srinagar plummeted to –6°C from 5°C,
recorded earlier. During the same time period, temperature in Chandigarh fell to
4°C from 16°C. In which city was the temperature fall greater?

Solution: Fall in temperature in Srinagar = 5 – (–6) = 5 + 6 = 11°C
Fall in temperature in Chandigarh = 16 – 4 = 12°C

Since, 12°C > 11°C
Therefore, the fall in temperature was greater in Chandigarh.

Example 22: The pulse rate of a patient suffering from blood pressure suddenly shot up by 54
beats per minute. After taking some medicine, his pulse rate fell by 74 beats per
minute. It again rose by 30 pulse per minute and stabilized. Find the net change in
his pulse rate?

Solution: Net change in pulse rate = +54 – 74 + 30 = 84 – 74 = 10
Thus, the net change in pulse rate is 10 beats per minute.

EXERCISE 6.3

1. Subtract:
(a) 15 from –20 (b) –37 from 37 (c) 21 from 0 (d) 23 from –12

2. Evaluate:
(a) (–5) – (6) + (9) (b) 40 – (–30) + 10 – (–9) (c) –23 + 13 –17 + (–67)

(d) 54 – (–45) + (–12) + 0 (e) 50 – (–40) – (–2)
3. Add –78 to the difference of –56 and –89.
4. Fill in the blanks with >, < or =.

(a) (–4) + (–7) ______ (–4) – (–7) (b) (–23) – (–17) ______ (–17) – (–23)

Problems Related to Thinking Skills

1. Find the successor of –45.
2. Find the predecessor of –99.

3. A plane flies 990 km west of Mumbai and then 1,678 km east. How far is the plane from
Mumbai now?

4. The sum of two integers is –23. If one of these two integers is 9, what is the second
integer?
5. The temperature in Shimla was 4°C in the afternoon but at midnight the temperature fell
by 10°C. What is the temperature recorded at midnight?

6. A person is standing on a mountain cliff which is about 5,600 m above sea level. He drops
his tool bag, which reaches a valley that is 2,500 m below sea level. Find the shortest
distance between the man and his bag.

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