6.25 Запишите в десятичной записи числа: 3 4 9 8 21 98 1 a) 5, 10, 10, 100, 100, 100, 100, 1000, 12; 7 13 19 407 1 б) 324, 1000, 10000', 21, 100000', 320;

a) Запишем в десятичной записи числа:

$$5\frac{3}{10} = 5 + \frac{3}{10} = 5 + 0,3 = 5,3$$

$$7\frac{4}{10} = 7 + \frac{4}{10} = 7 + 0,4 = 7,4$$

$$9\frac{13}{100} = 9 + \frac{13}{100} = 9 + 0,13 = 9,13$$

$$8\frac{13}{100} = 8 + \frac{13}{100} = 8 + 0,13 = 8,13$$

$$21\frac{21}{100} = 21 + \frac{21}{100} = 21 + 0,21 = 21,21$$

$$98\frac{98}{100} = 98 + \frac{98}{100} = 98 + 0,98 = 98,98$$

$$1\frac{1}{100} = 1 + \frac{1}{100} = 1 + 0,01 = 1,01$$

$$100\frac{1}{1000} = 100 + \frac{1}{1000} = 100 + 0,001 = 100,001$$

$$12\frac{12}{1000} = 12 + \frac{12}{1000} = 12 + 0,012 = 12,012$$

б) Запишем в десятичной записи числа:

$$324\frac{7}{1000} = 324 + \frac{7}{1000} = 324 + 0,007 = 324,007$$

$$21\frac{19}{10000} = 21 + \frac{19}{10000} = 21 + 0,0019 = 21,0019$$

$$407\frac{407}{100000} = 407 + \frac{407}{100000} = 407 + 0,00407 = 407,00407$$

$$320\frac{1}{100000} = 320 + \frac{1}{100000} = 320 + 0,00001 = 320,00001$$

Ответ: a) 5,3; 7,4; 9,13; 8,13; 21,21; 98,98; 1,01; 100,001; 12,012; б) 324,007; 21,0019; 407,00407; 320,00001.