Question

Yesterday's temperature was 25°C and there's a 5°C drop in temperature today. Which expression is used to calculate today's temperature?

• A. ${25}^{\circ }-5^{\circ }$
• B. $5^{\circ }-{25}^{\circ }$
• C. both a and b

Answer 1

The correct option is A ${25}^{\circ }-5^{\circ }$

Yesterday's temperature $={25}^{\circ }$
Temperature drop $=5^{\circ }$

$\therefore$ Today's temperature $={25}^{\circ }-5^{\circ }$
$={20}^{\circ }$

Also, $5^{\circ }-{25}^{\circ }=-{20}^{\circ }$
Clearly, ${25}^{\circ }-5^{\circ }\ne 5^{\circ }-{25}^{\circ },$ as subtraction is not commutative.