Question

Susan is creating a solution. A formula for the solution calls for 7/10 mL of water. Susan wants to make 2/7 less of the solution than the formula creates.

How much water should Susan use?

Express your answer as a fraction in simplest form.

Answer 1

This could work like follows:

If the the resulting volume should be 2 / 7 less then prescribed then each ingredient (not only water) should be taken 2 / 7 less. I would start with subtracting 7/10 - 2/7 = ?

Answer 2

0.414285714

Answer 3

A common divisor for both terms could be e.g. 70 (by multiplying with 10).

Answer 4

By mutliplying the first (7/10) with 7 and the second (2/7) with 10 you would get: 49/70 - 20/70. Right? Can you verify?

Answer 5

yes

Answer 6

If correct then you could subtract them one from another and would then have not the decimal but the rational representation. This I believe what your teacher wants to see

Answer 7

29/70?

Answer 8

Yes!! This I believe should be it. In other words if you take 7/10 (3/10 less then the whole something) and from this volume takes 2/7 (a bit less then half) away the remaining is somewhere less then half.

Answer 9

And 29/70 can not be reduced. Because 29 is prime and you can divide it through 1 or 29 without remainder. This should be it.