Optical illusion sight test with a hidden image leaves the internet baffled (2)

The test is just the latest in a string of a popular brain teasers sweeping the net.

An image of an iPhone screen became an internet sensation last week as thousands of people deliberated over the photo, which was widely shared along with the question: 'How many threes can you see in this picture?'

Social networkers came up with the most common answers of either 15, 19 or 21. But which answer is correct?

Can you count how many threes are on the iPhone screen? If you see 15, 19 or 21 number threes, you have arrived at the same conclusion as the majority of social networkers... but what's the correct answer?

There are in fact 19 number threes pictured in the image, but there could be 21 depending on how you interpret the question.

Apart from the eight threes in the phone number, there are two threes on the key pad as the number eight button has been replaced.

At 3.33pm, the time also contains three number threes and the battery power at 33 per cent contains another two.

That totals 15, the answer many social networkers have come to. On closer inspection, however, there are a further four hidden digits, totaling 19.

Three of the letters in the contact's name have been replaced with threes and the letter 'I' on the number four key has also been replaced.

But many online posts give the answer to be 21, with people seeming convinced that there are a further two threes in the image.

The differing opinions come down to the interpretation of the question. The images has been widely shared on Facebook and Twitter with the message. 'How many threes do you see in this picture?'

Many users have included the network bar and WiFi signal, both of which show three bars. But whether 19 or 21 is the correct answer is a matter of opinion.

The puzzle, which has been widely shared on Facebook and Twitter after resurfacing again online, has instigated heated debate - with many left flummoxed at how others arrive at a different answer.

Twitter user Dani posted: 'This thing annoyed the hell out of me when someone said 21. I was like no there's 18 until I looked again properly haha.'

How many threes can you see? Apart from the eight threes in the phone number, there are two threes on the key pad as the number eight button has been replaced. At 3.33pm, the time also contains three number threes and the battery power at 33 per cent contains another two. Three of the letters in the contact's name have been replaced with threes and the letter 'I' on the number four key has also been replaced.

Facebook Ravi Vidyadhar Pathak came to a grander total and said: '28 if it's saying to count everything that resembles to 3 including the network signal which is 3 dots the page info on left which is 3 the buttons having 3 letters ABC.'

Another philosophical Facebook user Marc Joseph posted: 'I see only 2....and technically am correct cause you never asked how many 3's are there in the pic.'

Athene Whitfield finally concluded the answer was 19 but had made so many previous guesses she posted: 'I got to that in the end but thought - I can't send an answer through again!!? Was getting embarrassed!'

One user by the name of Sarah was so involved in the problem she posted a mock-up of the screen with the potential answers highlighted in purple.

When a friend posted 'Not sure where you get 20 from' she posted: 'Now I'm not sure.'

It follows an optical illusion poster featuring tigers that resurfaced online this week, asking viewers to guess how many animals it featured.