Evaluate 390mm to 13cm as a ratio in its lowest term

First, change 13 cm to mm. Or you could change 390 mm to cm. What is that number?

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Originally Posted by wondergirl

first, change 13 cm to mm. Or you could change 390 mm to cm. What is that number?

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What number you talking

Change mm to cm, or change cm to mm. Doesn't matter. You want mm and mm or cm and cm.

390 mm = x cm?

It is perhaps easier to convert the bigger unit into the small unit.

390 mm : 13 cm

Convert 13 cm into mm, recall that 1 cm is equivalent to 10 mm.
Then, replace 13 cm (by the number of mm that you just get) into the ratio.
Simplify by taking out common factors.

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