关于先乘后除的问题

[zimo1213]

    @Test
    public void test() throws Exception {
        ExpressRunner runner = new ExpressRunner(true, true);
        DefaultContext<String, Object> context = new DefaultContext<>();
        context.put("a", 5006d);
        context.put("b", 7d);
        context.put("c", 28d);
        Object r = runner.execute("a * b / c", context, null, true, true);
        Object r2 = runner.execute("a / c * b", context, null, true, true);

        System.out.println(r);
        System.out.println(r2);
        System.out.println(5006d * 7d / 28d);
        System.out.println(5006d / 28d * 7d);
    }

得到结果
1251.5000000000
1251.49999999990
1251.5
1251.5

为什么先乘后除 和 先除后乘 结果不一致呢

3.3.4