Can a high internal resistance 9v battery be applied in parallel to 3vDC battery D cell amps pack to run a 10 amp 6V DC headlight bub at full brightness? Neither source power by itself can run bulb. Superimposed 2 sources to operate load bulb resistance? 9 volts DC added to separate power pack. A variable power resistor + amp meter can substitute for bulb, as a higher current reading obtained.

 

No.
You can't get something for nothing.
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.
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That does not follow the superposition theorem principle.

 

Can a high internal resistance 9v battery be applied in parallel to 3vDC battery D cell amps pack to run a 10 amp 6V DC headlight bub at full brightness? Neither source power by itself can run bulb. Superimposed 2 sources to operate load bulb resistance? 9 volts DC added to separate power pack. A variable power resistor + amp meter can substitute for bulb, as a higher current reading obtained.

If you put a 9 V battery in parallel with a 3 V battery pack, all that will happen is that charge will be transferred from 9 V battery to the 3 V pack until the voltages are equalized, and this won't take long. You are essentially trying to charge the 3 V back from the 9 V battery. If the 3 V pack is made up of non-rechargeable batteries, they won't like this and could do bad things, like leak or even catch fire (probably unlikely at the current that a typical 9 V alkaline battery can deliver). The 9 V battery will heat up significantly, though, and bad things might happen to it, too. Even if nothing really bad happens, you will deplete the 9 V battery in very short order, leaving you with a 3 V battery pack in which the batteries have probably been damaged to some degree.

 

I just assumed that the 9v battery IF, put in series, would not allow the ground of the 3volts battery pack to pass the higher amps, as the 9v has much higher internal resistance.

 

I just assumed that the 9v battery IF, put in series, would not allow the ground of the 3volts battery pack to pass the higher amps, as the 9v has much higher internal resistance.

You didn't ask about putting them in series, you asked about putting them in parallel.

If you put them in series, you have a 12 V source with an effective internal resistance dominated by the 9 V battery and an effective capacity that is basically the same as the 9 V battery.

In either case, making a voltage source by connecting 9 V and D cells is almost certainly not going to do what you would like it to do.

A typical D-cell alkaline isn't intended to deliver more than about 500 mA of current (and, at that, will be depleted in something like 12 to 18 hours). You can pull more, but the effective capacity drops pretty quick. So if you want to pull 10 A, you need somewhere around 20 batteries in parallel, and then you need to put four sets of these in series to get to you 6 V. So you can expect to use something like 80 batteries and you will drain them in less than a day.