Question

On Serena's tenth birthday, her mom was 3 times Serena's age. How old will Serena and her mom be when here mom's age times 0.5 will equal Serena's age? (I think there is a typo in my book. If so, I think this is the question they meant to ask/type. How old will Serena and her mom be when Serena's ages times 0.5 equals her mom's age? Basically, a x 0.5 = b)

Answer 1

So Serena is 10, and her mother is 3 times ten, so her mother is 30. And if we take 30 minus 10 we will have the age of the mom when Serena was born, which is 20. So we know that when Serena is 20, her mother will be 40. So when Serena is 20, she will be half of her mother's age. 40 × 0.5 = 20.