What are Missing Information Questions?
The math or reasoning part of your test may include questions that ask you about missing information.
In other words, you will be asked what piece of information is needed in order to solve a problem.
For these types of questions, you will not find a mathematical answer.
Rather, you have to evaluate the information provided by using logic and reasoning.
Then, you have to decide which detail is needed in order to have sufficient information to solve the problem.
So, missing information problems are also called logical deduction questions.
Is There Missing Information?
(1) Read the problem below and answer the question that follows.
Sandra left home at 11:30 am to go to her sister’s house. She drove at a constant speed of 60 miles per hour during her entire journey. First, she drove 100 miles to Anniton. She then rested for 20 minutes before driving 100 miles further to Madison. She got gas in Madison before driving to her sister’s house. What time was it when she arrived at her sister’s house?
What piece of information is needed in order to solve the problem?
A. The speed limit on the roads to her sister’s house.
B. The amount of time that it took Sandra to travel to Anniton.
C. The amount of money she spent on gasoline in Madison.
D. The amount of time she spent at the gas station in Madison.
E. Her normal departure time when traveling to her sister’s house.
The problem is asking us what information is required in order to determine the time Sandra arrived at her sister’s house.
STEP 1: In order to determine the arrival time at a new destination, we need to know the time the person began the journey and the amount of time he or she traveled.
From the problem, we know that Sandra left home at 11:30 am.
STEP 2: In order to know the amount of time a person travels, we need to know the amount of miles traveled and the speed.
The problem tells us that she drove 200 miles in total at a constant rate of 60 miles per hour.
STEP 3: Determine which information is missing.
In order to determine the arrival time, we would need to know the amount of time that a person spent during rest breaks.
We know that Sandra took a 20-minute rest break in Anniton.
However, we do not know the amount of time she took during her break at the gas station in Madison.
So, the correct answer is D.
Which Piece of Information is Missing?
(2) Read the problem below and answer the question that follows.
Soon Li walked half a mile to her neighbor’s house. It took her 10 minutes to make this journey. From her neighbor’s house, Soon Li walked a third of a mile into town. What is Soon Li’s average walking speed per hour for these two journeys?
What piece of information is needed in order to solve the problem?
A. The distance from Soon Li’s house into town.
B. The amount of time Soon Li stayed at her neighbor’s house.
C. Whether Soon Li walked or jogged.
D. The length of Soon Li’s stride in feet and inches.
E. The amount of time it took Soon Li to go from the neighbor’s house into town.
To calculate the average pace or speed, we need to know the speed for each part of the journey.
In order to calculate the walking speed per hour, we need to know the distance walked and the amount of time for the entire journey.
The problem tells us that Soon Li walked half a mile to her neighbor’s house, and it took her 10 minutes to make this journey.
Therefore, we have both the distance traveled and the amount of time for the first journey.
The problem also states that Soon Li made a second journey, walking a third of a mile into town from his neighbor’s house.
So, we have the distance traveled for the second journey, but we do not have the amount of time for the second journey.
So, the correct answer is E.