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I've got two related questions:
1) How do you say numbers in scientific notation in Japanese? For example, 3x108 is spoken in English as "three times ten to the eight". Do negative exponents works the same as ordinary negative numbers (i.e. prefix with マイナス)?
2) How do you say the units? For example m s-1 ("meters per second" - you get no prize for guessing why I'm asking ;) ), or more complicated examples like kg m2 s-2 K-1 ("kilogram metres squared per second squared kelvin").
1) three times ten to the eight = 3[掛]{か}ける10の8[乗]{じょう}
For negative, insert マイナス before the (number)乗, after the の.
2) ms^-1 = メートル[毎秒]{まいびょう}
kg m^2 s^-2 K^-1 = ジュール[毎]{まい}ケルビン
To supplement Tokyo Nagoya's answer, I found several Japanese references with long lists of examples that may be useful: how to read SI derived units, measurement units, and mathematical notation (including operators).
I would not claim to be an expert on this matter, but as for linking together multiple units, according to the lists I have linked, the approach seems to be similar to that in English. For example:
cal/h・m・deg = カロリー毎時毎メートル毎度 (calories per hour per metre per degree)
One small difference could be the way s^-2 is more commonly read as 毎秒毎秒 (per second per second) instead of 毎平方秒 (per square second), in contrast to m^-2 = 毎平方メートル and m^-3 = 毎立方メートル.
N = mkg/s^2 = メートルキログラム毎秒毎秒 (metres kilogram per second per second)
A literal reading of kg m^2 s^-2 K^-1 would probably then be キログラム平方メートル毎秒毎秒毎ケルビン.
