Page 27 - Start Up Mathematics_7

5. Simplify:
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(a) 19 + [{–20 × (55 – 13 – 3)} ÷ (–5)] (b) 38 – 2(5 – 8 – 3) ÷ [2{7 + (–3) × (–4)}]
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6. The temperature of a piece of metal is –13°C. On heating, the temperature of the metal rises
to 63°C:

(a) What is the change in temperature of the metal piece?
(b) What temperature of the metal would be exactly midway between the two temperatures
(the initial and final)?

(c) Calculate the temperature of the metal if it rises by 63°C.

Thinking Skills

1. Gaurav’s bank balance was ` 2,000. In a month he deposited ` 300, ` 750 and ` 450 and
issued cheques worth ` 700 and ` 1,250. Find the balance in Gaurav’s account at the end of
the month?
2. Imagine that you are a fighter pilot flying a jet aircraft at an altitude of 20,000 feet. You lower
the aircraft by 7,000 feet and then raise it by 5,000 feet. What is the net change in the altitude?
Also find the altitude after the two changes.
3. Raghuraj has 30 marbles. In 5 games he won 3 marbles each and in 7 games he lost 2 marbles
each. Find the marbles Raghuraj has at the end of the games.
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4. To convert temperature from Celsius to Fahrenheit, we multiply by and add 32, i.e.,
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9C
F = +32. Find the Fahrenheit temperature that corresponds to:
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(a) –15°C (b) 40°C (c) –40°C

5. Give an example to show that the following properties are not true for integers.
(a) Closure property for division (b) Associative property for division

(c) Commutative property for subtraction (d) Distributive property of division over addition
6. In a Microbiology laboratory, certain tests are done under controlled temperature. The variation
in temperature is by fixed number of degrees per minute. Evaluate each of the following:

(a) The temperature at the beginning of an experiment is 20°C. It increases by 4°C per minute.
What is the temperature at the end of the experiment if it took 15 minutes to complete?
(b) The temperature is made to fall by 3°C per minute. The temperature at the end of an
experiment is –7°C, which took 13 minutes to complete. What was the temperature at
the beginning of the experiment?

7. A pharmaceutical company prepares different types of injections and medicinal creams which
are stored at a fixed range of temperatures.
The names of these injections are coded as INJ-T20, INJ-F308 and INJ-58R.

The given graph shows the temperatures, in degrees Celsius at which these are to be stored.
Using the information, find the injections and medicinal creams that can be stored in a place
where the variation in temperature is as follows.

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