Comp Sci Scratch codes -- Find the value of a at the end of the program

[Tesla In Person]

Homework Statement

Find the value of a at the end of the program

Relevant Equations

No need of equations

Hi, i am really new to scratch programming so I am having difficulties in interpreting how does this code work ? I understand the first block set a = 5. But i don't know what is that " Repeat 10 " block. What does it do? So really stuck at that "repeat 10" so haven't gone further.

 

[Office_Shredder]

I think it's saying do the following block of code 10 times in a row.

 

[Tesla In Person]

I think it's saying do the following block of code 10 times in a row.

Ok so if i set a=1. Then a <3 so a*2 = 1*2 = 2. If i repeat this process 10 times , what do i have to do with the a value each time. Add them up ? 2 *10= 20 which is option c) which is wrong. The correct answer is e) 15.

 

[pbuk]

Ok so if i set a=1.

There is no instruction set a to 1, the instruction inside the loop is change a by 1. What is the value of a the first time it reaches this instruction?

 

[Tesla In Person]

There is no instruction set a to 1, the instruction inside the loop is change a by 1. What is the value of a the first time it reaches this instruction?

I thought "change a by 1" meant replace the value of 5 by 1.
"What is the value of a the first time it reaches this instruction?"- 5?

 

[pbuk]

I thought "change a by 1" meant replace the value of 5 by 1.

You are not the first person to have been caught out by that, it's a confusing "feature" of Scratch.

"What is the value of a the first time it reaches this instruction?"- 5?

Yes.

 

[Tesla In Person]

You are not the first person to have been caught out by that, it's a confusing "feature" of Scratch.

Yes.

So we add 1 ? It becomes 6 and 6 is not smaller then 3 so we go back and keep adding 1 ? Repeating this 10 times gives a=15 which is correct.

 

[Mark44]

I thought "change a by 1" meant replace the value of 5 by 1.

No, as already mentioned. There's a difference between "set" and "change by". "Set" replaces the old value of the variable by some new value. "Change by" adds or subtracts some value to a variable. In the program "change a by 1" adds 1 each time in the loop. If it had said "change a by -2" it would have subtracted 2 each time in the loop.

what do i have to do with the a value each time. Add them up ? 2 *10= 20 which is option c) which is wrong. The correct answer is e) 15.

In the program, a's value is always >= 5, so the if condition is never executed. Essentially what the code does is to increase a (which starts off at 5) by 1 ten times, which results in a's final value being 15.

 

[FactChecker]

I believe there are tutorials for Scratch that are easy and would introduce these basic Scratch statements.
I Googled it and this looks like one.