How to randomise multiple questions within a block

One way to go about this would be as follows:
Create 16 Loop and Merge blocks. They'll loop over your set of 200 and display only one randomly. You can then put these 16 blocks in a randomizer and display only 6. Your setup would be something like this:
Q1: One of the 16 questions (each block will contain a unique entry)
Q2: Piped from Loop and Merge
Q3: Same across all

However, if you know JavaScript, then it can be simplified much more.

Hi ahmedA !
Thanks so much for responding. I am, however, still a little confused.
So yes, I can create 16 blocks for question 1 (which is just a static image not requiring a response), and use a randomiser in the survey flow to pick a random one.
And I have now played around a bit with Loop and Merge - and that would work for Q2 - which is just a maths problem. So I can enter 200 (I hope) maths problems (eg: 72 + 16 = ) and have these presented in a random order.
But... when I then start the next block - it cannot use the same maths problems as the participant has seen previously. And this doesn't seem to be possible. What I really need, I guess, is for Qualtrix to insert an item (in random order) from a large pool and keep track (across multiple blocks) which items have been used.
I'll try and explain what I need to do a bit better.
Block A:
Q1: 1 Image presented - selected randomly from 16 images.
Q2: 1 math problem presented and a text field for entry. This should come from a large (200 say) pool of maths problems.
Q3: A generic question about the image presented in Q1.
: repeat this 6 times.
Block B
Q1: 1 Image presented - selected randomly from a DIFFERENT pool of 16 images.
Q2 - 1 math problem presented and a text field for entry. From the SAME large (200 say) pool of maths problems.
Q3: A generic question about the image presented in Q1.
: repeat this 6times.
etc...
But for all these different blocks - they can never show the same maths problem.
Would your solution work for this? Am I just not understanding your solution correctly?
Thanks again,
Dan.

You have partially understood my answer correctly.
However, you had not specified that you want to items from pool B to also be exclusive (ref your original post).
You need to be more specific, at present your math problems appear to be attention checks. If that's the case, is there a requirement that they come from a set of 200 or could they just be random.
If they are random, might as well generate random numbers.

Taking both of your posts into account, here's what I understand:
You want to show an image, ask a question about it and an attention check.
If that's the case, just put your 16 images in a loop and merge, and only show 6 randomly.

Hi ahmedA !
Ah sorry - for not explaining myself more clearly.
The thing I am building is a psych experiment into Cognitive load. I want to present a visual task of varying complexity - in conjunction with math tasks of a consistent difficulty throughout. Then I will ask people to rate the difficulty of the two tasks together. This for each block participants will be asked to do the following 4 times:
1) Memorise a pattern of dots in a grid. (must be unique). (this induces Cognitive load for the duration of the block - and while they carry out step 2.
2) Answer a math problem (must be unique). These must be carefully constructed to be similar to one another in processing - so cannot use RNGs.
3) Recreate the pattern of dots on the grid they saw in step 1.
Each 'block' (in experimental language now - not Qualtrix 'blocks') will consist of 4 repetitions of the above tasks.
There will be 7 blocks in all (each consisting of 4 repititions) and in each block Q1 patterns will come from a different pool of stimuli. Eg: Block 1: 3 dots patterns, Block 2: 4 dots patterns, etc... The maths problems will be the same for all blocks.
Within each block (not qualtrix block), Q1 will draw from a different pool of visual stimuli - and none may repeat.
Within the entire experiment - the math tasks will all draw from a common pool - and none may repeat.
Here's a graphic representation of this:

Regards,
Dan.