The cost C of hiring a lorry is partly constant and partly varies with the time T spent. If it cost ₦850 for 4 hours hire and ₦1300 for 7 hours hire, find the cost for 12 hours.

$1800

Step-by-step explanation:

First, rewrite out the information you already have:

-for 4 hrs-cost $850

-for 7 hrs-cost $1300

-for 12 hrs-$?

Next, we have to find out the amount of cost for hire per hour, so we can multiply that by 12 hrs:

-start by subtracting $850 from $1300:

1300-850=$450

-now subtract 4 hrs from 7 hrs:

7-4=3 hrs

In doing this, we see that the cost for 3 hrs hire is $450.  Now, to find the unit cost per hr hire, divide $450 by 3 hrs:

450÷3=$150/hr

It costs $150 per hr hire.

Now, we have to find the cost for 12 hrs hire, so just multipy the unit cost by 12:

150*12=$1800 for 12 hrs hire

It costs $1800 for 12 hrs hire.

the system of inequalities is

step-by-step explanation:

step 1

find the equation of the dashed line

we have the points

(0,0) and (3,1)

the line passes through the origin, so, is a direct variation

find the slope

the equation of the dashed line is

the solution of the inequality a s the shaded area above the dashed line

therefore

the equation of the inequality a is

step 2

find the equation of the solid line

we have the points

(4,0) and (0,4)

find the slope

the equation of the solid line is

the solution of the inequality b s the shaded area below the solid line

therefore

the equation of the inequality b is

step 3

the system of inequalities is