What Is the Maximum Voltage for a Circuit with Series and Parallel Resistors?

[knobles8179]

Homework Statement

A 2.7 kOhms and a 3.8 kOhms resistor are connected in parallel; this combination is connected in series with a 1.5 kOhms resistor.
If each resistor is rated at 0.9 W (maximum without overheating), what is the maximum voltage that can be applied across the whole network?

Homework Equations

parallel resistors 1/Req = 1/R1 + 1/R2 + 1/R3 ...
resistors in a series Req = R1 + R2 + R3 +...
Vab = E- IR
I= V/Req

The Attempt at a Solution

i have no idea. please help!

 

[rl.bhat]

Using the formula for wattage
w = I^2*R, find the current in resistance in series.
This is the current drawn from the battery.
Using this current, check the wattage of the individual resistance in the parallel combination. If it is less than 0.9 W, proceed further to find the total resistance of the circuit. Then V = I*Req.
If not, find the current in the individual resistance in the parallel combination for 0.9 w dissipation. Take the minimum current for finding the maximum voltage supply.