The ratio of cement to sand for mortar is 1: 3. if sandy puts in 7 shovels of cement, how many shovels of sand should she put in?

Let x be the amount of cement and y be the amount of sand. If the ratio of cement to sand for mortar is 1:3, then and y=3x.

So, if Sandy puts in x=7 shovels of cement, then she puts shovels of sand.

21 shovels of sand.

Set this up as a proportion with cement on top and sand on bottom.  Our proportions will look like this then: .  Cross multiply to get x = 21.  So 21 shovels of sand is needed.

The answer is 109 times per second

Yes you do, so £1973.09 - £1473.50 = £499.59 so tim overpaid £499.59 .hope this ; )