Question

A. using substitution find the value of the remaining unknown in each of the following formulas.

1.t=rs (s + 1) if r=4 and s=5
2.k=6-5q/2g if q=3 and g=8
3.p=a+b-2c if a=2, b=-1 and c=5
4.l=1/x - 2/y + z if x=4, y=6, and z=2/3

Answer 1

Substitution means that we need to replace some of the variables by the given values.

1) t = rs*(s + 1) (if r=4 and s=5)

So we just need to replace r by 4 and s by 5 in the equation.

t = 4*5*(5 + 1) = 20*6 = 120

t = 120

2) k = 6 - 5q/2g (if q=3 and g=8)

We need to replace q by 3, and g by 8.

k = 6 - (5*3)/(2*8) = 6 - 15/16 = 5.167

k = 5.167

3) p = a + b - 2c (if a = 2, b = -1, c = 5)

Replacing the variables we get:

p = 2 + (-1) - 2*(5)

p = 2 - 1 - 10 = -9

p = -9

4) I = 1/x - 2/y + z (if x = 4, y = 6, and z = 2/3)

Replacing the variables we get:

I = 1/(4) - 2/(6) + (2/3)

I = 1/4 - 2/6 + 2/3 = 1/4 - 1/3 + 2/3

I = 1/4 + 1/3 = 3/12 + 4/12 = 7/12

I = 7/12 = 0.583