Thanks for letting me know about Mandarin. Did not know that about Singapore - thought Mandarin was the official language.
Malay is the national language. I just wiki-ed

Well don't believe everything you read on wiki then. There are 4 official languages of Singapore: English, Mandarin Chinese, Malay and Tamil. But the most widely spoken is English (although amongst the local population it is a colloquial version known as Singlish, which incorporates direct translations from Hokkien Chinese, which is probably the most common Chinese language here.)
My kids learnt Mandarin for about 5 years. Did quite well at pre-school, where there were Mandarin speaking teachers around most of the time, but lost it once they went to UWC and have since transferred onto Spanish.
You can easily live in Singapore for 10 years and never have to speak anything other than standard English, though it does take a while to tune into and understand the local pattois.