Answer:
3. 12 airplanes and 6 cars
4. 30 swirled marbles and 22 solid marbles
Step-by-step explanation:
In each case, it is easy enough to check the offered answer to see if it matches problem requirements.
3. You are correct.
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4. All answers total 52 marbles, so we need to check to see which has 8 more swirled marbles.
a) 28 more swirled marbles
b) 28 fewer swirled marbles
c) 8 fewer swirled marbles
d) 8 more swirled marbles -- as required by the problem
The correct choice is the last one: 30 swirled marbles; 22 solid marbles.
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The first step in solving any problem is to understand what the problem is and what a solution will look like. When the questions are multiple-choice, it is often easier to check the choices than to solve the problem from scratch. Knowing what the solution must look like often lets you eliminate half or more of the answer choices, simplifying the remaining checking.
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Both of these are "sum and difference" problems. You are given the total of two items and the difference between them. The generic solution is that the larger quantity is half the sum of the two given numbers.
For 3, this means the number of airplanes (the larger quantity) is half of 18+6=24, so is 12. The number of cars is 6 less than that: 12-6=6.
For 4, this means the number of swirled marbles (the larger quantity) is half of 52+8=60, so is 30. The number of solid marbles is 8 less than that: 30-8=22.
