Multiple choice How many vacuum tubes were used in ENIAC? 15000 18000 19000 21000 Reveal answer Fill a bubble to check yourself B Correct answer Explanation ENIAC (Electronic Numerical Integrator and Computer), built in 1945, contained approximately 18,000 vacuum tubes. This massive number contributed to its enormous size of about 1,800 square feet and high power consumption of 150 kilowatts.