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# Constructing numerical expressions

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.