Virtual Gate Test Series: Digital Logic - Carry Look Ahead Adder

Question

In a $4-$bit carry look ahead adder, the propagation delay of EX-OR gate is $20ns,$ AND and OR gates is $10ns.$ The sum and carry output of full adder takes $20ns$ and $10ns$ respectively. The total propagation delay of the above adder in $ns$ is

Comments

May be this helps you.

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@mcjoshi what does this mean " The sum and carry output of full adder takes 20ns and 10ns respectively ".

the information provided in previous sentence was sufficient

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first information is about gates and second one about adder and $4-bit$ adder requires $3-full$ and $1-half$ adder.

Answer 1

Generated terms and prop. terms work in parallel. Look at the image attached.