Mr.Johnson sold 20 cartons of noodles.
<u>SOLUTION:
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Given, Mr. Johnson imported some cartons of noodles. There were 28 packages of noodles in each carton.
He then sold 10 packages of noodles for
He received from the sale of noodles.
Now, we know that, for noodles packages
Then, for (let it be) n noodles packages
So, by criss cross method,
Therefore, he sold 560 noodle packages.
Now, we know that, 28 packages 1 carton
Then, 560 packages (let it be ) m cartons
So, by criss cross method,
Hence, he sold 20 cartons.