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Sal solves a word problem by constructing a numerical expression.  Created by Sal Khan.
Video transcript
Alan found 4 marbles to add to his 5 marbles currently in his pocket. He then had a competition with his friends and tripled his marbles. Write a numerical expression to model the situation without performing any operations. So let's think about what's going on. So he already had 5 marbles in his pocket. So he already had 5 marbles in his pocket. And then he found 4 more marbles to add to that. So we can add the 4 marbles to the 5 marbles. So 4 marbles plus the 5 marbles. So that's what happened after the first sentence. He found 4 marbles to add to his 5 marbles currently in his pocket. He then had a competition with his friends and tripled his marbles. So this is how many marbles he had before tripling, and now he's tripling, now he's tripling his marbles. So we'd wanna multiple 3 times the total number of marbles he has now, times 4 plus 5. So this right over here is the numerical expression that models the situation without any, without performing any operations. We of course could then actually calculate this. He now has, he has 9 marbles before tripling and then you multiply it by 3, and he has 27. But this is what they're asking for. They want us, they want us to write this expression.