You are on a cycling trip around Europe with friends. You want to cycle to a nearby lake. Your friend says it is 15 km away. Whi
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Answer:
Sarah is 13 years old
Step-by-step explanation:
Represent Sarah's age with S
Her first brother's age with F
Her second brother's age with B
So, we have:
From the first statement, we have:
---- (1)
From the second, we have:
---- (2)
The product of their ages is 40.
First, we make F the subject in (1) and B the subject in (2)
Their product is represented as follows:
Substitute values for F and B
Open bracket
Subtract 40 from both sides
Factorize:
Split:
or
But Sarah's age can't be 0 because she has two younger brothers.
So, we stick to
Make S the subject
<em>Hence, Sarah is 13 years old</em>