OK, Ok, let me explain...

Your pot noodle nutritional information does say that there are 150kcals per 100g
HOWEVER when you add water the weight of your yummy 'Bad Boy' increases to 385grams so at 150kcal per 100gram you need to multiply that by 3.85 giving you 550kcals!!!!
Who says the intellectual level of the Thumper club only extends to Landrovers, weathergirls and gas stoves!! ... we can solve the mystery of the pot noodle too!!!!!
( ....well we can with a bit of help from the official Pot Noodle website

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