Why gas efficiency saves money in Blockchain / Solidity - Challenge Your Understanding

Challenge - 5 Problems

❓ Predict Output

intermediate

Gas cost difference between two functions

Consider two smart contract functions that perform the same task but with different gas usage. What is the output showing the gas cost difference?

Blockchain / Solidity

functionA() uses 50000 gas units
functionB() uses 30000 gas units
Gas price is 20 gwei
Calculate the cost difference in gwei.

A 1000000 gwei

B 200000 gwei

C 600000 gwei

D 400000 gwei

💡 Hint

Multiply the gas units difference by the gas price.

The difference in gas units is 20000. Multiplying by 20 gwei gives 400000 gwei saved.

🧠 Conceptual

intermediate

Why does gas efficiency save money?

Which of the following best explains why improving gas efficiency in smart contracts saves money?

A Because gas price decreases when contracts are efficient

B Because using less gas reduces the total fee paid for executing the contract

C Because less gas used means fewer transactions per block

D Because efficient contracts run faster on the blockchain nodes

💡 Hint

Think about how gas relates to transaction fees.

Gas efficiency reduces the amount of gas consumed, which directly lowers the transaction fee paid.

🔧 Debug

advanced

Identify the gas inefficiency in this Solidity code

Which line in the code below causes unnecessary gas usage? contract Example { uint[] public data; function addData(uint x) public { for(uint i = 0; i < data.length; i++) { if(data[i] == x) { return; } } data.push(x); } }

A The data.push(x) call

B The return statement inside the loop

C The for loop iterating over data array

D The public visibility of data array

💡 Hint

Loops over dynamic arrays cost gas proportional to their length.

Iterating over the entire data array every time addData is called uses more gas as the array grows.

📝 Syntax

advanced

Which code snippet correctly reduces gas usage by avoiding storage writes?

Choose the code snippet that saves gas by minimizing storage writes in Solidity.

A

uint count;
function increment() public {
  count++;
}

B

uint count;
function increment() public {
  uint temp = count;
  temp++;
  count = temp;
}

C

uint count;
function increment() public {
  count = count + 1;
}

D

uint count;
function increment() public {
  uint temp = count + 1;
  count = temp;
}

💡 Hint

Look for the simplest way to update a variable.

Using count++ directly is the simplest and most gas-efficient way to increment a storage variable.

🚀 Application

expert

Calculate total gas cost for multiple transactions

A smart contract function costs 45000 gas per call. You plan to call it 100 times. The gas price is 25 gwei. What is the total cost in gwei?

A 112500000 gwei

B 1125000 gwei

C 4500000 gwei

D 225000000 gwei

💡 Hint

Multiply gas per call by number of calls, then by gas price.

Total gas = 45000 * 100 = 4,500,000 gas units. Total cost = 4,500,000 * 25 = 112,500,000 gwei.