Question

The temperature on a certain morning is'$-11°\mathrm{C}$‘ at ’$5\mathrm{am}$‘. If the temperature drops ’$3°$‘ by ’$6\mathrm{am}$‘ and rises ’$5°$‘ at ’$8\mathrm{am}$‘ and again drops ’$3°$‘ at ’$9\mathrm{am}$‘, what is the temperature at ’$9\mathrm{am}$'?

Answer 1

Given: The temperature on a certain morning is '$-11°\mathrm{C}$‘ at ’$5\mathrm{am}$'.

Step 1: Find the temperature at $6\mathrm{am}$:

By '$6\mathrm{am}$‘, the temperature drops ’$3°$',

So, the temperature at $6\mathrm{am}$$=-11-3$ ($\because$Temperature drop is denoted by ‘$-$’ and temperature gain is denoted by ‘$+$’ sign)

$=-11+\left(-3\right)$ ($\because$ In subtraction, we add the additive inverse of the number to be subtracted)

$=-14°\mathrm{C}$ ($\because$ The sum is negative when both the integers are negative)

Step 2: Find the temperature at '$8\mathrm{am}$',

The temperature rises $5°$ at '$8\mathrm{am}$',

So, the temperature at $8\mathrm{am}$$=-14+5$

$=-9°\mathrm{C}$ ($\because \left|14\right|>\left|5\right|$, So we shall subtract $5$ from $14$ and will use the sign of $14$)

Step 3: Find the temperature at $9\mathrm{am}$:

The temperature drops $3°$ at '$9\mathrm{am}$‘, So the temperature at ’$9\mathrm{am}$'$=-9-3$

$=-9+\left(-3\right)$

$=-12°\mathrm{C}$

Therefore, the temperature at '$9\mathrm{am}$' is $-12°\mathrm{C}$