Answer:
1 kg of baking soda costs $4.50.
Explanation:
Write and solve an equation of ratios, as follows:
4/9 kg $2
------------- = --------------
1 kg x
Multiplying both numerators by 9, we get:
4 kg $18
------------ = ---------
1 kg x
Cross-multiplying, we get 4x kg = $18-kg. Solving for x, we get:
$18-kg
x = -------------- = $4.50
4kg
1 kg of baking soda costs $4.50.