Imagine you’re in a place where the temperature drops by 5°C each hour. Class 7

Imagine you’re in a place where the temperature drops by 5°C each hour. Class 7

Question 1.

Imagine you’re in a place where the temperature drops by 5°C each hour. If the temperature is currently at 8°C, write an expression which denotes the temperature after 4 hours. Class 7

Solution:

8°C - 5°C - 5°C - 5°C - 5°C = -12°C

Question 2.

Find 3 consecutive numbers with a product of (a) - 6, (b) 120. Class 7

Solution:

-3, -2, -1; 4 × 5 × 6.

Question 3.

An alien society uses a peculiar currency called ‘pibs’ with just two denominations of coins — a + 13 pibs coin and a - 9 pibs coin. You have several of these coins. Is it possible to purchase an item that costs + 85 pibs?

Yes, we can use 10 coins of+13 pibs and 5 coins of - 9 pibs to make a total of + 85. Using the two denominations, try to get the following totals :

(a) + 20

(b) + 40

(c) - 50

(d) + 8

(e) + 10

(f) - 2

(g) + 1

[Hint: Writing down a few multiples of 13 and 9 can help.]

(h) Is it possible to purchase an item that costs 1568 pibs?

Solution:

(a) 5 coins of 13 pibs and 5 coins of -9 pibs.

(b) 10 coins of 13 pibs and 10 coins of -9 pibs.

(c) 10 coins of 13 pibs and 20 coins of -9 pibs.

(d) 2 coins of 13 pibs and 2 coins of -9 pibs.

(e) 7 coins of 13 pibs and 9 coins of -9 pibs.

(f) 11 coins of 13 pibs and 16 coins of -9 pibs.

(g) 7 coins of 13 pibs and 10 coins of -9 pibs.

(h) Yes. By using 117 coins of 13 pibs and 3 coins of -9 pibs.