Three types of tea each worth $6.00 / lb, $7.50 / lb and $x / lb are mixed in proportion of 1 : 2 : 3 to form a mixture worth $8.50 / lb. What is the value of x in $ / lb?
The Usual Method
Let the quantities of each type of $6.00, $7.50 and $x of tea be 1 lb, 2 lbs and 3 lbs respectively as per their proportions.
Hence total worth of tea =
Hence cost / lb =
This is equal to $8.50 / lb
Estimated Time to arrive at the answer = 60 seconds.
Observe that if two types of tea of $6 and $7.50 to be mixed with a third type of $x to form a mixture costing $8.50, the cost of the third type of tea should be more than $8.50. This means that you can eliminate all other options except ‘5’ i.e. $10 which is the answer.
Estimated Time to arrive at the answer = 5 seconds.