This may be a stupid question. But, why is D includes abc and c includes ba and so on?

Question

This may be a stupid question. Why is D includes abc and c includes ba and so on?

Thanx a lot for the answer. And can you please give me some tips how i can improve my intuition? I struggle a lot with word problems. Is there a way to get good at it, or is it just a talent or is it just practice?

Comments

Here are some tips.

Draw a picture if you can. This helps you to turn a problem into something visual and concrete, instead of abstract and mysterious.

Go through the wording carefully and logically. Reword the question if necessary. Digest the question. Note the facts.

In word problems, it's sometimes beneficial to go to the end of the problem and work backwards.

Look for the sentence that asks you to find something, and give it a label, an algebraic letter, perhaps the letter that is the initial of what you are asked to find. Then take this algebraic quantity and treat it as if you knew the answer. That is, go back to the word problem and operate on the algebraic quantity (as if it were a number) by building up algebraic expressions until eventually the problem presents you with an actual number. So you then have an expression and a given number you can equate the expression to. You should now be able to solve for the unknown algebraic quantity.

When you have what you think is the solution, go through the problem again using your solution just to make sure you haven't made a mistake. A common mistake is to add when you should have subtracted, or vice versa.

A common word problem is one involving ages and time expressions such as so many years ago (subtract the number of years) or so many years hence (add the number of years).

Good luck with your next word problem!

Answer 1

It's not a stupid question. Those mothers who have 4 or more children also have more than 1 child, more than 2 children and more than 3 children. Those who have 3 or more children exclude those with only one child or only two children, but include those with 4 or more. Those who have 2 or more children exclude those with only one child, but include those with 3 or more and 4 or more. As the number of children rises, there are fewer mothers. The largest figure has to include all the groups. Imagine you can separate the mothers into the four groups then look at the whole picture. Put the groups side by side: A (1 child), B (2 children), C (3 children), D (4+ children). Now ask how many mothers have 3 or more children (for example). You can see that it's groups C and D. The difference between C and D must be those mothers with 3 children. You can apply the same logic to the other groups and so arrive at the figures for the individual groups. I tried to keep the solution concise so perhaps in doing so I confused you.

Answer 2

Help much appreciated. Will definitely try this out.