No, neither is true. Although the majority of Arabs are Muslims, the majority of Muslims are not Arabs.
The terms Arab and Muslim are often found together, for the Arab region holds the origins of Islam. However, an Arab is an individual who resides, or whose heritage is from the Arab region (e.g. Iraq, Kuwait, Jordan) This does not make them Muslim.
To follow, a Muslim is an individual who embraces the Islamic tradition, or the religion Islam, thus their mother tongue can be any language, their heritage can be from any country. Thus, one could be a Hindu Arab, a Jewish Arab, a Muslim Arab, a Muslim Australian. The two terms are not inherently joined.
According to the Pew Research Center’s Mapping the Global Muslim Population, the largest population of Muslims in one country is Indonesia (202,867,000), followed by Pakistan (174,082,000) and India (160,945,000). In fact, over 60% of the world population of Muslims reside in the Asia-Pacific region. In contrast, only 4.6million, or 0.4% live in the Americas.
Pew Research Center. (2009). Mapping the Global Muslim Population. Pew Forum. Accessed 03-05-2015. Available at http://www.pewforum.org/2009/10/07/mapping-the-global-muslim-population/